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B2 verb /oʊˈmɪt/

omit

omitir
Meaning
to leave out or exclude; to fail to include something
Example
Please don't omit any important details from your report.
Por favor, no omitas detalles importantes de tu informe.
C2 noun /ˌɔːrnɪˈθɒlədʒɪst/

ornithologist

ornitólogo
Meaning
a scientist who studies birds
Example
The ornithologist spent years studying migratory birds.
El ornitólogo pasó años estudiando aves migratorias.
C1 verb /ˌoʊvərˈpaʊər/

overpower

dominar
Meaning
To defeat or gain control over someone or something by using greater strength or force.
Example
The soldiers managed to overpower the enemy forces.
Los soldados lograron dominar las fuerzas enemigas.
A1 verb, adjective /oʊn/

own

poseer
Meaning
to possess something; belonging to oneself
Example
She owns a beautiful house in the city.
Ella posee una hermosa casa en la ciudad.
C1 noun /oʊˈmɪʃ.ən/

Omission

omisión; exclusión
Meaning
the action of excluding or leaving out someone or something; a failure to include
Example
The omission of his name from the list was intentional.
La omisión de su nombre de la lista fue intencional.
B1 verb /ˈɔːrɡənaɪz/

organize

organizar
Meaning
to arrange systematically; to plan and coordinate
Example
She organized a surprise party for her friend.
Ella organizó una fiesta sorpresa para su amiga.
C1 adjective /əˈblɪɡ.ə.tɔː.ri/

obligatory

obligatorio
Meaning
Required by a legal, moral, or other rule; compulsory.
Example
Wearing a seatbelt is obligatory in most countries.
Usar el cinturón de seguridad es obligatorio en la mayoría de los países.
B2 noun /ˈɑp.tə.mɪst/

Optimist

optimista
Meaning
a person who tends to be hopeful and confident about the future; someone who sees the good side of things
Example
As an optimist, she always believed things would improve.
Como optimista, siempre creyó que las cosas mejorarían.
B2 noun ˈɒksɪdʒən prəˈdʌkʃən

oxygen production

producción de oxígeno
Meaning
The process of generating oxygen through photosynthesis or other means.
Example
Plants are vital for oxygen production and the maintenance of life.
Las plantas son vitales para la producción de oxígeno y el mantenimiento de la vida.
B1 noun /əˈpɪn.jən/

Opinion

opinión
Meaning
a view or judgment formed about something; a belief or assessment based on grounds short of proof
Example
In my opinion, this is the best solution.
En mi opinión, esta es la mejor solución.
B2 noun /ˈɔr.fən/

Orphan

huérfano
Meaning
a child whose parents are dead; someone without protective support
Example
The orphan was adopted by a loving family.
El huérfano fue adoptado por una familia amorosa.
B2 adverb /ˌoʊvərˈnaɪt/

Overnight

de la noche a la mañana; de repente; muy rápidamente
Meaning
during the night; suddenly; very quickly
Example
The city was transformed overnight.
La ciudad fue transformada de la noche a la mañana.
C2 noun ˌɒbfəsˈkeɪʃən

obfuscation

ofuscación, confusión
Meaning
The action of making something obscure, unclear, or unintelligible.
Example
The obfuscation of the data made it difficult to interpret.
La ofuscación de los datos dificultó su interpretación.
C1 noun /oʊθ/

Oath

juramento
Meaning
a solemn promise or declaration; a sworn statement
Example
The doctor took an oath to help patients.
El doctor hizo un juramento de ayudar a los pacientes.
A1 adjective /oʊld/

old

viejo
Meaning
having lived for a long time; not new or young
Example
He still drives his old car.
Él todavía conduce su coche viejo.
C1 adverb /ˈaʊtwədli/

Outwardly

externamente; superficialmente;
Meaning
on the surface; externally; in appearance
Example
Outwardly, he seemed calm, but inside he was nervous.
Exteriormente, parecía tranquilo, pero por dentro estaba nervioso.
C2 adjective /əˈfɪʃəs/

officious

entrometido
Meaning
Excessively eager to offer unwanted help or advice; meddlesome.
Example
The officious guard kept interrupting the visitors with unnecessary instructions.
El guardia entrometido interrumpía a los visitantes con instrucciones innecesarias.
C1 noun /ˈoʊvərˌsiːər/

overseer

supervisor
Meaning
a person who supervises work or workers; a manager
Example
The overseer made sure the workers followed safety rules.
El supervisor se aseguró de que los trabajadores siguieran las reglas de seguridad.
C2 noun /ɔːˈreɪʃən/

oration

discurso
Meaning
A formal speech, especially one given on a ceremonial occasion
Example
The president delivered an inspiring oration.
El presidente dio un discurso inspirador.
C2 adjective /ɑːlˈfæktəri/

olfactory

olfatorio
Meaning
Relating to the sense of smell.
Example
The perfume activated her olfactory nerves immediately.
The perfume activated her olfactory nerves immediately.
C1 adjective /ˌɒmnɪˈprezənt/

omnipresent

omnipresente
Meaning
(of God) present everywhere at the same time.
Example
Social media has become an omnipresent force in modern society.
Las redes sociales se han convertido en una fuerza omnipresente en la sociedad moderna.
A1 noun/adjective/adverb /ˌaʊtˈsaɪd/

outside

afuera
Meaning
the external part or surface of something; beyond the boundary
Example
Children were playing outside in the yard.
Los niños estaban jugando afuera en el jardín.
C1 noun /ˈɒktəɡən/

octagon

octágono
Meaning
A polygon with eight sides and eight angles.
Example
The stop sign is shaped like an octagon.
La señal de alto tiene forma de octágono.
C2 adjective /ˈɒfɪʃ/

offish

distante
Meaning
Unfriendly, distant, or reserved in manner.
Example
He seemed offish at the party and avoided most conversations.
Parecía distante en la fiesta y evitaba la mayoría de las conversaciones.
B2 noun /oʊk/

oak

roble
Meaning
a large tree that produces acorns and has strong, hard wood
Example
The old oak tree provided shade for the entire yard.
El viejo roble dio sombra a todo el jardín.
B2 verb /ˌoʊvərˈduː/

overdo

exagerar
Meaning
to do something too much; to exaggerate or carry to excess
Example
Don't overdo the exercise on your first day at the gym.
No exageres con el ejercicio en tu primer día en el gimnasio.
B2 adjective, verb /əbˈskjʊr/

obscure

oscuro
Meaning
Not clearly expressed or understood; to make something difficult to see or understand.
Example
The meaning of the poem was obscure to most readers.
El significado del poema era oscuro para la mayoría de los lectores.
B1 noun /ˌɒp.əˈtjuː.nə.ti/

opportunity

oportunidad
Meaning
A favorable chance or set of circumstances that makes it possible to do something.
Example
She seized the opportunity to study abroad.
Ella aprovechó la oportunidad de estudiar en el extranjero.
C1 adjective /əˈkʌlt/

occult

oculto
Meaning
Relating to mysterious, supernatural, or magical powers and practices.
Example
She had always been fascinated by the occult and its hidden knowledge.
Ella siempre estuvo fascinada por lo oculto y su conocimiento oculto.
C2 adjective /ˈoʊ.vɔɪd/

ovoid

ovoide
Meaning
egg-shaped; resembling an oval or ellipse
Example
The artist painted an ovoid shape in the center of the canvas.
El artista pintó una forma ovoide en el centro del lienzo.
A2 adjective /ˈɒb.vi.əs/

Obvious

obvio; fácil de entender
Meaning
easily perceived or understood; clear and apparent to the mind
Example
It was obvious that she was upset about something.
Era obvio que ella estaba molesta por algo.
C2 verb /ˌoʊvərˈliːp/

overleap

saltar por encima
Meaning
To jump over something; to omit or disregard something.
Example
He managed to overleap the fence easily.
Él logró saltar la cerca fácilmente.
C1 noun /ˌɒbstəˈtrɪʃən/

obstetrician

obstetra
Meaning
A doctor specializing in pregnancy, childbirth, and women's reproductive health.
Example
The obstetrician monitored the mother’s health throughout the pregnancy.
El obstetra monitoreó la salud de la madre durante el embarazo.
B1 noun ˌɔː.ɡən.aɪˈzeɪ.ʃənz

organizations

organizaciones
Meaning
Organized groups of people with a particular purpose
Example
Organizations play a key role in policymaking.
Las organizaciones desempeñan un papel clave en la toma de decisiones políticas.
C1 adjective /ˌaʊtˈspoʊkən/

Outspoken

franco
Meaning
frank; speaking directly
Example
She is known for being outspoken about social issues.
Es conocida por ser franca sobre los problemas sociales.
C2 noun /ˈaʊtˌrɪɡər/

outrigger

estructura de refuerzo
Meaning
a projecting structure on a boat, used for stability, or a boat fitted with such support
Example
The fisherman paddled his outrigger canoe across the lagoon.
El pescador remó su canoa con outtrigger a través de la laguna.
C2 noun /ˌɒn.əˌmæt.əˈpiː.ə/

onomatopoeia

onomatopeya
Meaning
The formation of a word from a sound associated with what is named.
Example
The word 'buzz' is an example of onomatopoeia.
La palabra 'zumbido' es un ejemplo de onomatopeya.
B1 noun /ˈɑb.stə.kəl/

Obstacle

obstáculo
Meaning
something that blocks or makes progress difficult; a barrier
Example
Bad weather was the main obstacle to our journey.
El mal tiempo fue el principal obstáculo para nuestro viaje.
C1 adjective /ɒmˈnɪv.ər.əs/

Omnivorous

omnívoro
Meaning
eating both plants and animals; feeding on various kinds of food
Example
Bears are omnivorous animals that eat both plants and meat.
Los osos son animales omnívoros que comen tanto plantas como carne.
C2 adjective /ˈoʊdiəs/

odious

odioso
Meaning
extremely unpleasant or repulsive
Example
The dictator was remembered for his odious crimes.
El dictador fue recordado por sus odiosos crímenes.
C1 adjective /ˈaʊt.kɑːst/

Outcast

rechazado
Meaning
rejected by society; excluded person
Example
He felt like an outcast in his new school.
Él se sintió como un rechazado en su nueva escuela.
B1 adjective /əˈbiː.di.ənt/

Obedient

obediente
Meaning
willing to comply with orders or instructions; submissive
Example
The obedient student always follows the teacher's instructions.
El estudiante obediente siempre sigue las instrucciones del profesor.
C2 adjective /ˈɒpjʊlənt/

opulent

opulento
Meaning
Ostentatiously rich, luxurious, or lavish.
Example
They hosted an opulent wedding with gold decorations.
Organizaron una boda opulenta con decoraciones doradas.
C2 noun /oʊd/

ode

oda
Meaning
a lyrical poem, often expressing praise or strong emotions
Example
The poet wrote an ode to the beauty of nature.
El poeta escribió una oda a la belleza de la naturaleza.
C1 noun /ˈɑd.ɪ.ti/

Oddity

rareza
Meaning
something that is strange or unusual; a peculiar trait
Example
His habit of sleeping standing up was considered an oddity.
Su hábito de dormir de pie se consideraba una rareza.
A1 pronoun /aʊər/

our

nuestro
Meaning
belonging to or associated with the speaker and one or more other people
Example
This is our house.
Esta es nuestra casa.
B2 adjective ɔːrˈɡæn.ɪk

organic

orgánico
Meaning
Produced or involving production without the use of chemical fertilizers, pesticides, or other artificial agents.
Example
Organic farming improves soil health and reduces pollution.
La agricultura orgánica mejora la salud del suelo y reduce la contaminación.
C1 verb /aʊst/

oust

destituir
Meaning
To remove someone from a position or place of power or authority.
Example
The rebels ousted the dictator from power.
Los rebeldes destituyeron al dictador del poder.
C1 verb /əˈprɛs/

oppress

oprimir
Meaning
to keep someone down by harsh and unfair use of authority; to suppress
Example
The dictator oppressed the people for decades.
El dictador oprimió a la gente durante décadas.
C1 adjective /ˈəʊnərəs/

onerous

arduo
Meaning
involving a great deal of effort, difficulty, or burden
Example
Fulfilling the contract proved to be an onerous task for the company.
Cumplir el contrato resultó ser una tarea ardua para la empresa.
C1 adjective /əbˈtjuːs/

Obtuse

tonto; obtuso; lento de comprensión
Meaning
annoyingly insensitive or slow to understand; lacking in intelligence or perception
Example
He was being deliberately obtuse about the instructions.
Él estaba siendo deliberadamente obtuso sobre las instrucciones.
B2 noun /ˌɔː.ri.enˈteɪ.ʃən/

orientation

orientación
Meaning
the process of becoming familiar with a new situation or environment
Example
The company provides an orientation for all new employees.
La empresa ofrece una orientación para todos los nuevos empleados.
A1 adjective /ˈɔːr.ɪndʒ/

Orange

naranja
Meaning
having a color between red and yellow like that of a ripe orange fruit
Example
The orange sunset painted the sky magnificently.
El atardecer naranja pintó el cielo magníficamente.
C1 adjective /ˈɒm.ɪ.nəs/

Ominous

ominoso; amenazante
Meaning
giving the impression that something bad will happen; threatening; foreboding
Example
The dark clouds looked ominous before the storm.
Las nubes oscuras se veían ominosas antes de la tormenta.
B2 adjective /ˌɔːɡənaɪˈzeɪʃənəl/

organizational

organizacional
Meaning
relating to the structure or arrangement of a company or group
Example
He works on improving the organizational structure of the company.
Él trabaja en mejorar la estructura organizacional de la empresa.
B2 noun /ˈaʊtskɜːrts/

outskirts

afueras de la ciudad
Meaning
The outer parts of a town or city, away from the center.
Example
They moved to the outskirts of the city for a quieter life.
Se mudaron a las afueras de la ciudad para una vida más tranquila.
C1 verb /ˌoʊvərˈθroʊ/

overthrow

felicidad
Meaning
To remove a leader or government from power, often by force.
Example
The rebels planned to overthrow the corrupt regime.
No pudo esconder su felicidad cuando recibió el premio.
C1 adjective /ˈɒptɪməm/

optimum

óptimo
Meaning
Most conducive to a favorable outcome; best.
Example
To achieve optimum results, we need to improve efficiency.
Para lograr los mejores resultados, necesitamos mejorar la eficiencia.
C1 adjective /ˌoʊvərˈrɔt/

overwrought

angustiado / excesivamente nervioso
Meaning
extremely agitated or nervous; excessively elaborate
Example
She was too overwrought to speak clearly after the accident.
Ella estaba demasiado angustiada para hablar claramente después del accidente.
C2 noun /ˈɔɪl.mən/

Oilman

petrolero
Meaning
a person who works in the oil industry; someone who sells oil or petroleum products
Example
The oilman discovered a new oil field in the desert.
El petrolero descubrió un nuevo campo petrolero en el desierto.
C1 verb /ˈɒfsɛt/

offset

compensar
Meaning
To counterbalance or compensate for something.
Example
The company's losses were offset by gains in other departments.
Las pérdidas de la compañía fueron compensadas por las ganancias en otros departamentos.
C2 adjective /ˈɒkjʊlər/

ocular

ocular
Meaning
Relating to the eye or vision.
Example
The patient was referred to a specialist for ocular treatment.
El paciente fue referido a un especialista para tratamiento ocular.
C1 noun /ˌɑːpərˈtuːnɪst/

opportunist

oportunista
Meaning
A person who takes advantage of situations for personal gain, often disregarding principles.
Example
He is seen as an opportunist who always puts his interests first.
Se le ve como un oportunista que siempre pone sus intereses primero.
C1 verb /ɔːrˈdeɪn/

ordain

ordenar
Meaning
To officially make someone a priest or minister; to decree or order something officially.
Example
The bishop will ordain three new priests this Sunday.
El obispo ordenará tres nuevos sacerdotes este domingo.
C2 noun /ˈɒrɪz(ə)n/

orison

oración
Meaning
a prayer, especially a devout or formal one
Example
He whispered a quiet orison before going to sleep.
Susurró una oración tranquila antes de dormir.
C2 noun ˈoʊʃən ˌstrætɪfɪˈkeɪʃən

ocean stratification

estratificación oceánica
Meaning
The formation of layers in ocean water due to differences in density.
Example
Ocean stratification affects marine biodiversity.
La estratificación oceánica afecta la biodiversidad marina.
A2 noun /ˈoʊ.ʃən/

ocean

océano
Meaning
A very large expanse of sea, especially the main areas of sea between continents.
Example
The ocean covers more than 70% of the Earth's surface.
El océano cubre más del 70% de la superficie de la Tierra.
B1 adverb /əˈrɪdʒɪnəli/

originally

originalmente
Meaning
in the beginning, at first
Example
Originally, she wanted to be a doctor.
Originalmente, ella quería ser doctora.
C1 adjective/adverb /ˌɒfˈhænd/

offhand

sin pensar
Meaning
Without previous thought or preparation; casual and sometimes dismissive.
Example
She gave an offhand reply to his serious question.
Ella dio una respuesta sin pensarlo a su seria pregunta.
C1 noun /ˈɔr.ə.kəl/

Oracle

oráculo
Meaning
a person regarded as a source of wise counsel; in ancient times, a priest or priestess acting as a medium
Example
The ancient Greeks consulted the oracle at Delphi.
Los antiguos griegos consultaban el oráculo en Delfos.
C2 verb /əbˈtruːd/

obtrude

obstruir
Meaning
to force oneself or one's ideas into a situation uninvited or inappropriately
Example
He didn’t want to obtrude into their private conversation.
Él no quería obstruir su conversación privada.
C2 verb /ˈɑːblɪˌɡeɪt/

obligate

obligar
Meaning
to bind legally or morally; to compel someone to do something
Example
The contract obligates the company to provide timely service.
El contrato obliga a la empresa a proporcionar un servicio puntual.
C1 noun /oʊˈveɪʃən/

ovation

ovación
Meaning
an enthusiastic show of approval, especially by clapping hands
Example
The actor received a standing ovation after his performance.
El actor recibió una ovación de pie después de su actuación.
C2 noun /ˈoʊdiəm/

odium

odio
Meaning
general or widespread hatred or disgust directed toward someone as a result of their actions
Example
The scandal brought public odium on the corrupt minister.
El escándalo trajo odio público al ministro corrupto.
B2 noun oʊˈbiː.sə.t̬i

obesity

obesidad
Meaning
The condition of being grossly fat or overweight.
Example
Obesity increases the risk of diabetes and heart disease.
La obesidad aumenta el riesgo de diabetes y enfermedades cardíacas.
B2 noun ˈɔː.bɪt

orbit

órbita
Meaning
The curved path of a celestial object around a star, planet, or moon.
Example
The satellite maintains its orbit around Earth.
El satélite mantiene su órbita alrededor de la Tierra.
B2 adjective /ˈɒp.tɪ.məl/

optimal

óptimo, más favorable
Meaning
Best or most favorable; the most effective under particular conditions.
Example
The optimal temperature for plant growth is around 25°C.
La temperatura óptima para el crecimiento de las plantas es de alrededor de 25°C.
C2 noun /əˈprəʊ.bri.əm/

opprobrium

desprecio, oprobio
Meaning
Harsh criticism or public disgrace.
Example
The scandal brought opprobrium on the politician.
El escándalo trajo desprecio al político.
B2 adjective /ˈɔː.rəl/

Oral

oral; relacionado con la boca
Meaning
spoken rather than written; relating to the mouth
Example
The oral examination will test your speaking skills.
El examen oral evaluará tus habilidades de hablar.
C2 adjective /ɒmˈnɪp.ə.tənt/

omnipotent

omnipotente
Meaning
Having unlimited power; able to do anything; all-powerful.
Example
In many religions, God is considered omnipotent.
En muchas religiones, Dios se considera omnipotente.
C1 adjective /oʊˈbiːs/

obese

obeso
Meaning
Extremely overweight; having an excessive amount of body fat.
Example
The doctor advised the obese patient to adopt a healthier lifestyle.
El doctor le recomendó al paciente obeso adoptar un estilo de vida más saludable.
B1 noun ˌɔː.ɡən.aɪˈzeɪ.ʃən

organization

organización
Meaning
An organized group of people with a particular purpose, such as a business or government department.
Example
The organization was officially inaugurated in 2024.
La organización fue inaugurada oficialmente en 2024.
B2 noun /ˈɔːkɪstrə/

orchestra

orquesta
Meaning
a large group of musicians playing different instruments together
Example
The orchestra performed beautifully at the concert.
La orquesta actuó maravillosamente en el concierto.
C1 verb /ˌaʊtˈduː/

outdo

superar
Meaning
To do better than someone else; to surpass.
Example
She always tries to outdo her classmates in exams.
Ella siempre trata de superar a sus compañeros de clase en los exámenes.
C1 noun /ˈəʊ.nəs/

onus

responsabilidad
Meaning
A duty or responsibility, especially a heavy one.
Example
The onus is on the government to provide relief to the victims.
El ónus está en el gobierno para proporcionar alivio a las víctimas.
C1 noun /ˌɑːk.sɪˈmɔːr.ɒn/

oxymoron

oxímoron
Meaning
a figure of speech where two contradictory terms are combined
Example
The phrase 'deafening silence' is a classic oxymoron.
La frase 'silencio ensordecedor' es un oxímoron clásico.
C2 noun /ˈoʊpiət/

opiate

opiáceo
Meaning
a drug containing opium or its derivatives, used to relieve pain or cause sleep
Example
The doctor prescribed an opiate to relieve the patient's pain.
El médico recetó un opiáceo para aliviar el dolor del paciente.
C1 noun /ˈoʊ.mən/

Omen

presagio de buena o mala suerte futura
Meaning
an event regarded as a sign of future good or bad luck
Example
Many people consider a black cat crossing your path a bad omen.
Muchas personas consideran que un gato negro cruzando tu camino es un mal presagio.
C2 verb ˈɑːb.fə.skeɪt

obfuscate

ofuscar, oscurecer, confundir
Meaning
Render obscure, unclear, or unintelligible.
Example
Politicians often obfuscate facts to mislead people.
Los políticos a menudo ofuscan los hechos para engañar a la gente.
B2 noun /ˈoʊ.dər/

Odour

olor
Meaning
a distinctive smell, especially an unpleasant one
Example
The odour of fresh bread filled the kitchen.
El olor de pan fresco llenó la cocina.
C2 adjective /ɒmˈnɪʃ.ənt/

Omniscient

omnisciente
Meaning
having complete knowledge; all-knowing
Example
The narrator in the novel appears to be omniscient, knowing every character's thoughts.
El narrador en la novela parece ser omnisciente, conociendo todos los pensamientos de los personajes.
B1 adjective /ˈaʊtər/

outer

exterior
Meaning
situated on or toward the outside; external
Example
The outer layer of the jacket is waterproof.
La capa externa de la chaqueta es impermeable.
B1 noun ˈɒk.sɪ.dʒən

oxygen

oxígeno. Un gas incoloro e inodoro, esencial para la vida.
Meaning
A colorless, odorless reactive gas, the chemical element of atomic number 8 and the life-supporting component of the air.
Example
Oxygen is vital for life.
El oxígeno es vital para la vida.
C1 verb /ˈoʊvərˌhɔːl/

overhaul

revisión completa
Meaning
to examine thoroughly and repair or improve something that is worn or ineffective
Example
The company decided to overhaul its outdated computer system.
La compañía decidió hacer una revisión completa a su sistema de computadoras obsoleto.
C1 noun /ˈɑːdəsi/

odyssey

viaje largo
Meaning
a long, adventurous journey; a series of experiences
Example
Her career has been an odyssey of challenges and achievements.
Su carrera ha sido una odisea de desafíos y logros.
B2 noun ˈaʊt.pʊt

output

producción
Meaning
The amount of something produced by a person, machine, or industry.
Example
Climate change reduces agricultural output.
El cambio climático reduce la producción agrícola.
C2 noun /ˈoʊvərlɔːrd/

overlord

señor
Meaning
A ruler, master, or person of great power and authority over others.
Example
The peasants were forced to pay taxes to their overlord.
Los campesinos fueron obligados a pagar impuestos a su señor.
B2 noun /ˈɒp.tɪ.mɪ.zəm/

optimism

optimismo
Meaning
Hopefulness and confidence about the future or the successful outcome of something.
Example
Her optimism helped her overcome difficult times.
Su optimismo le ayudó a superar tiempos difíciles.
B2 noun /ˈaʊtˌfɪt/

outfit

conjunto de ropa
Meaning
A set of clothes worn together, often for a particular occasion.
Example
She wore a beautiful outfit to the party.
Ella usó un hermoso conjunto de ropa para la fiesta.
C2 adjective /ˈɒsiəs/

osseous

óseo
Meaning
consisting of or turned into bone; bony
Example
The fossil showed osseous structures of the ancient creature.
El fósil mostró estructuras óseas de la antigua criatura.
C1 noun /əbˈzɜːvəns/

observance

observancia
Meaning
The practice of following a custom, rule, or religious law.
Example
The festival is held in observance of a centuries-old tradition.
El festival se celebra en observancia de una tradición centenaria.
C1 noun /əˈkɜr.əns/

Occurrence

suceso
Meaning
an instance or event of something happening; the fact of occurring
Example
The occurrence of earthquakes is common in this region.
La ocurrencia de terremotos es común en esta región.
C1 verb /ˈɒp.tɪ.maɪz/

optimize

optimizar
Meaning
To make the best or most effective use of a situation, opportunity, or resource.
Example
The company is working to optimize its supply chain.
La empresa está trabajando para optimizar su cadena de suministro.
B2 noun /ˈaʊt.breɪk/

Out-break

brote
Meaning
a sudden occurrence or eruption of something, especially disease or violence
Example
The outbreak of flu affected many students in the school.
El brote de gripe afectó a muchos estudiantes en la escuela.
C2 noun /ˌɔːrəˈtɔːri.oʊ/

oratorio

composición musical religiosa
Meaning
A large-scale musical composition for orchestra, choir, and soloists, usually on a sacred theme, performed without costumes or scenery.
Example
Handel's 'Messiah' is one of the most famous oratorios ever written.
El 'Mesías' de Handel es uno de los oratorios más famosos jamás escritos.
B2 noun/verb /ˌoʊvərˈlæp/

overlap

solapamiento
Meaning
To extend over and cover partly; an area where things coincide.
Example
The two meetings overlap by an hour.
Las dos reuniones se solapan por una hora.
A2 noun /ˈɒf.ɪs/

office

oficina
Meaning
a room or building where people work, usually at desks
Example
She left the office early to attend a family event.
Ella dejó la oficina temprano para asistir a un evento familiar.
C2 verb /ˈɑːskjʊleɪt/

osculate

besar
Meaning
To kiss.
Example
They osculated under the mistletoe during the party.
Ellos se besaron debajo del muérdago durante la fiesta.
C1 noun /ˈɔɪntmənt/

ointment

ungüento
Meaning
A smooth, oily substance applied to the skin for healing or soothing.
Example
The doctor prescribed an ointment for the burn on his arm.
El doctor recetó un ungüento para la quemadura en su brazo.
A2 adjective /ˈɔː.dɪ.nər.i/

Ordinary

ordinario; común; no especial
Meaning
normal; usual; not special
Example
It was just an ordinary day at the office.
Era solo un día ordinario en la oficina.
A2 adjective /ɒd/

Odd

extraño; inusual; diferente de lo que es normal o esperado
Meaning
strange; unusual; different from what is normal or expected
Example
That's an odd way to solve the problem.
Esa es una forma extraña de resolver el problema.
C2 noun /ˈɑːbəlɪsk/

obelisk

obelisco
Meaning
A tall, four-sided, narrow tapering monument with a pyramid-shaped top.
Example
The ancient Egyptians built obelisks to honor their gods.
Los antiguos egipcios construyeron obeliscos para honrar a sus dioses.
C1 adjective /ˌɒbsəˈliːt/

obsolete

obsoleto
Meaning
No longer in use or out of date.
Example
Floppy disks are now completely obsolete.
Los disquetes ahora están completamente obsoletos.
B2 verb /ˌoʊvərˈsiː/

oversee

supervisar
Meaning
to supervise or watch over something; to manage and direct
Example
The manager will oversee the entire construction project.
El gerente supervisará todo el proyecto de construcción.
A2 noun /ˈɔr.dər/

Order

orden; secuencia
Meaning
a command or instruction; the arrangement of things following a particular sequence
Example
The teacher gave an order to sit down quietly.
El maestro dio una orden para sentarse tranquilamente.
C1 verb /aʊtˈlæst/

outlast

perdurar más tiempo que
Meaning
to continue longer than; to endure beyond someone or something else
Example
The old castle has outlasted many generations.
El viejo castillo ha perdurado más que muchas generaciones.
B2 noun /ˈɔːɡənɪzəm/

organism

organismo
Meaning
a living thing that has an organized structure and can grow and reproduce
Example
Every organism needs water to survive.
Todo organismo necesita agua para sobrevivir.
C1 adjective /ɒˈstɛnsəbl/

ostensible

aparente
Meaning
stated or appearing to be true, but not necessarily so
Example
His ostensible reason for leaving was illness, but many doubted it.
Su aparente razón para irse era la enfermedad, pero muchos lo dudaron.
A2 noun /ˈʌn.jən/

Onion

cebolla
Meaning
a round vegetable with a strong taste and smell, made up of many layers
Example
I need to chop some onions for the curry recipe.
Necesito cortar algunas cebollas para la receta de curry.
C1 noun /ˈaʊtpoʊst/

outpost

puesto avanzado
Meaning
A small military camp or position at some distance from the main force, used especially as a guard.
Example
The soldiers were stationed at a remote outpost.
Los soldados fueron apostados en un puesto avanzado remoto.
C1 adjective /əˈbliːk/

Oblique

oblicuo; diagonal; indirecto o evasivo
Meaning
slanting; diagonal; indirect or evasive
Example
The artist drew an oblique line across the canvas.
El artista dibujó una línea oblicua en el lienzo.