opportune
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C1 adjective /ˌɑːpərˈtuːn/

opportune

momento oportuno
Meaning
Happening at a suitable or convenient time.
Example
She arrived at an opportune moment to help.
Llegó en un momento oportuno para ayudar.
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 /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.
A2 noun /ˈɒm.lət/

Omelet

tortilla
Meaning
a dish made from beaten eggs cooked in a frying pan and often folded around a filling
Example
She made a cheese omelet for breakfast.
Ella hizo una tortilla de queso para el desayuno.
B2 noun /ˌɑb.zɚˈveɪ.ʃən/

Observation

observación
Meaning
the action of watching something carefully; a comment or remark
Example
The scientist made careful observations of the experiment.
El científico hizo observaciones cuidadosas del experimento.
B1 verb /əbˈzɜːrv/

observe

observar
Meaning
to watch carefully; to notice or perceive something
Example
Scientists observe the behavior of animals in the wild.
Los científicos observan el comportamiento de los animales en la naturaleza.
C1 adjective /əˈprɛs.ɪv/

Oppressive

opresivo
Meaning
Harsh and authoritarian; overwhelming; causing distress; tyrannical;
Example
The oppressive heat made it difficult to work outside during the summer.
El calor opresivo dificultaba trabajar afuera durante el verano.
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 noun (plural) /ˈɔːrdʒiːz/

orgies

orgías
Meaning
Wild gatherings involving excessive indulgence in food, drink, or sexual activity.
Example
The ancient Romans were infamous for their lavish feasts and orgies.
Los antiguos romanos eran infames por sus banquetes lujosos y orgías.
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.
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 /wʌn θɜːd/

one-third

un tercio
Meaning
one part of something that is divided into three equal parts
Example
One-third of the class was absent today.
Un tercio de la clase estaba ausente hoy.
C1 adjective /ˈɑp.ər.ə.tɪv/

Operative

activo; en efecto; funcionando; operativo;
Meaning
Functioning; in effect; working; active;
Example
The new safety protocols became operative immediately after the accident.
Los nuevos protocolos de seguridad se volvieron operativos inmediatamente después del accidente.
C2 verb /ˈoʊɡəl/

ogle

mirar lascivamente
Meaning
To look at someone with obvious sexual interest.
Example
He kept ogling the models on the runway.
Él no podía dejar de mirar las modelos en la pasarela.
C1 verb ˈɔː.kɪ.streɪ.tɪd

orchestrated

orquestado
Meaning
Planned or coordinated carefully and deliberately.
Example
The attacks were orchestrated with precision.
Los ataques fueron orquestados con precisión.
C2 verb /ˈɑːbdʒərˌɡeɪt/

objurgate

reprender severamente
Meaning
to scold or rebuke severely
Example
The teacher objurgated the student for being dishonest.
El maestro reprendió severamente al estudiante por ser deshonesto.
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.
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.
A2 verb /ˈɔːfər/

offer

ofrecer
Meaning
to present something for acceptance or rejection; to propose
Example
She offered to help with the project.
Ella se ofreció a ayudar con el proyecto.
B1 noun /ˈɒbstəkəlz/

obstacles

obstáculos
Meaning
Things that block one's way or prevent or hinder progress.
Example
Obstacles in life can often lead to valuable lessons.
Los obstáculos en la vida a menudo conducen a lecciones valiosas.
C2 noun /ˈɔː.rɪ.fɪs/

orifice

orificio
Meaning
an opening or hole, especially in the body or a device
Example
The medicine was applied through a small orifice in the device.
El medicamento se aplicó a través de un pequeño orificio en el dispositivo.
B1 noun /əˈkeɪ.ʒən/

Occasion

ocasión; evento especial
Meaning
a particular time or instance of an event; a special celebration
Example
Their wedding was a joyous occasion.
Su boda fue una ocasión alegre.
B2 noun /ˌɒb.zəˈveɪ.ʃənz/

observations

observación
Meaning
The action or process of observing something carefully.
Example
Observations of distant galaxies provide new insights.
Las observaciones de galaxias distantes proporcionan nuevas ideas.
C2 noun /ˈoʊ.vər.let/

Overlet

colchón adicional
Meaning
a thin mattress or pad placed over a bed for additional comfort
Example
The overlet makes the bed more comfortable to sleep on.
El overlet hace la cama más cómoda para dormir.
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.
C2 adjective /ˌoʊvərˈwiːnɪŋ/

overweening

excesivamente arrogante
Meaning
excessively arrogant or prideful
Example
His overweening pride cost him many friends.
Su exceso de orgullo le costó muchos amigos.
C2 noun /ˈɔːrdnəns/

ordnance

suministros militares
Meaning
Military supplies including weapons, ammunition, and combat equipment.
Example
The army stored ordnance in a secure facility outside the city.
El ejército almacenó suministros militares en una instalación segura fuera de la ciudad.
C1 verb /ˌaʊtˈweɪ/

outweigh

ser más importante
Meaning
To be more important, valuable, or significant than something else.
Example
The benefits of the new policy outweigh the risks.
Los beneficios de la nueva política superan los riesgos.
B2 adjective /ˈɔɪl.i/

Oily

oleoso; cubierto de aceite; grasoso
Meaning
covered with oil; containing oil; greasy
Example
Her oily skin needs special care.
Su piel aceitosa necesita cuidados especiales.
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.
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.
C1 noun /ɒpˈtɒmɪtrɪst/

optometrist

optometrista
Meaning
A healthcare professional who examines eyes and prescribes corrective lenses.
Example
The optometrist prescribed new glasses for her.
El optometrista le recetó nuevos anteojos.
B2 verb /əˈfend/

offend

ofender
Meaning
to cause displeasure or resentment; to hurt someone's feelings
Example
His rude comments offended many people at the meeting.
Sus comentarios groseros ofendieron a muchas personas en la reunión.
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.
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.
C1 noun ˈoʊʃən əˌsɪdɪfɪˈkeɪʃən

ocean acidification

acidificación oceánica
Meaning
The ongoing decrease in the pH of the Earth's oceans, caused by the absorption of carbon dioxide from the atmosphere.
Example
Ocean acidification is caused by atmospheric CO2 absorption.
La acidificación oceánica es causada por la absorción de CO2 atmosférico.
C2 noun /ˈɔːrdʒi/

orgy

fiesta desmedida
Meaning
A wild party involving excessive indulgence, especially of a sexual nature.
Example
The novel described a scandalous orgy in a wealthy mansion.
La novela describió una orgía escandalosa en una mansión rica.
C1 adjective /ɔːˈneɪt/

ornate

ornamentado
Meaning
elaborately or highly decorated
Example
The palace hall was filled with ornate furniture and paintings.
El salón del palacio estaba lleno de muebles ornamentados y pinturas.
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.
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.
B2 noun /ɒdz/

odds

probabilidad
Meaning
the likelihood or probability of something happening; chances for or against something
Example
The odds of winning the lottery are very low.
Las probabilidades de ganar la lotería son muy bajas.
B2 adjective /ˈaʊtˌɡoʊɪŋ/

outgoing

sociable
Meaning
Friendly and sociable; inclined to mix with others.
Example
He is an outgoing person who loves meeting new people.
Es una persona sociable a la que le encanta conocer gente nueva.
A2 noun /ˈɒpərə/

opera

ópera
Meaning
a dramatic performance in which the actors sing most of their lines
Example
We watched a beautiful opera at the theater last night.
Vimos una hermosa ópera en el teatro anoche.
C2 adjective /ˌoʊpəˈlɛsənt/

opalescent

opalescente
Meaning
showing or reflecting a milky, iridescent light like an opal
Example
The opalescent sky glowed with shades of pink and blue.
El cielo opalescente brillaba con tonos de rosa y azul.
C1 verb /əbˈstrʌkt/

obstruct

obstruir
Meaning
to block or hinder progress; to prevent or impede movement
Example
The fallen tree obstructed the road for several hours.
El árbol caído obstruyó el camino durante varias horas.
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 /ˌoʊvərˈsiːz/

overseas

en el extranjero
Meaning
in or to a foreign country across the sea
Example
He went overseas for higher education.
Él fue al extranjero para estudiar.
C2 noun /əbˈstɛtrɪks/

obstetrics

obstetricia
Meaning
The branch of medicine dealing with childbirth and care of women giving birth.
Example
She is studying obstetrics to become a specialist in childbirth.
Ella está estudiando obstetricia para convertirse en especialista en partos.
B2 verb /əˈrɪdʒɪneɪt/

originate

originar
Meaning
to come into existence; to begin; to create or produce
Example
The tradition originated in ancient times.
La tradición se originó en tiempos antiguos.
B2 verb /ˌoʊvərˈwɛlm/

overwhelm

abrumar
Meaning
to overpower someone emotionally or physically; to be too much to handle
Example
She was overwhelmed with gratitude after receiving the help.
Ella estaba abrumada de gratitud después de recibir la ayuda.
C1 adjective /oʊˈvɜːrt/

overt

abierto
Meaning
Done or shown openly; not hidden or secret.
Example
There was an overt display of hostility between the rivals.
Hubo una exhibición abierta de hostilidad entre los rivales.
C1 verb /əˈfɪʃieɪt/

officiate

oficiar
Meaning
To perform official duties, especially in a ceremony or as a referee.
Example
The priest will officiate the wedding ceremony.
El sacerdote oficiará la ceremonia de la boda.
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.
B2 adjective /aʊtˈreɪdʒəs/

outrageous

atroz
Meaning
Shockingly bad or excessive; very unusual or amusing.
Example
The comedian told an outrageous joke.
El comediante contó un chiste atroz.
B2 adjective; verb (past participle) /ˈɒkjʊpaɪd/

occupied

ocupado
Meaning
being in use or taken; filled or lived in; controlled or held by force
Example
The room is occupied, so please wait outside.
La habitación está ocupada, por favor espere afuera.
C2 noun /ˈɒlɪv brɑːntʃ/

olive-branch

rama de olivo
Meaning
A symbol of peace or reconciliation; an offer to end conflict.
Example
He extended an olive-branch to his rival after years of hostility.
Extendió una rama de olivo a su rival después de años de hostilidad.
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.
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 noun /ˈɑːlɪˌɡɑːrki/

oligarchy

oligarquía
Meaning
A small group of people having control of a country, organization, or institution.
Example
The nation was ruled by a wealthy oligarchy that controlled all resources.
La nación fue gobernada por una oligarquía rica que controlaba todos los recursos.
C1 noun ɔːrˈdiːl

ordeal

prueba difícil
Meaning
A physical or mental painful experience that must be endured
Example
Surviving the wilderness was a tough ordeal for them.
Sobrevivir en la naturaleza fue una dura prueba para ellos.
B1 adjective /ˈɔːɡənaɪzd/

organized

organizado
Meaning
Arranged in a systematic way, especially on a large scale.
Example
An organized approach to work increases productivity and reduces stress.
Un enfoque organizado para el trabajo aumenta la productividad y reduce el estrés.
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.
B2 noun /ˈɔɪ.stər/

Oyster

ostra
Meaning
a type of shellfish that can be eaten and sometimes contains pearls
Example
She ordered fresh oysters at the seafood restaurant.
Ella ordenó ostras frescas en el restaurante de mariscos.
C1 verb əˈblɪt.ə.reɪt

obliterate

destruir
Meaning
To destroy utterly; wipe out completely, to erase or remove something completely.
Example
The storm obliterated entire villages.
La tormenta destruyó aldeas enteras.
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.
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 verb /ˌoʊvərˈruːl/

overrule

anular
Meaning
to reject or disallow by exercising one's superior authority; to override a decision
Example
The judge overruled the objection from the defense attorney.
El juez anuló la objeción del abogado defensor.
B1 adjective /əˈkeɪ.ʒən.əl/

Occasional

ocasional
Meaning
occurring infrequently or irregularly; happening from time to time
Example
She enjoys occasional walks in the park.
Ella disfruta de paseos ocasionales en el parque.
B2 verb /ˈɒkjʊpaɪ/

occupy

ocupar
Meaning
to take up space or time; to live or work in a place
Example
The new family will occupy the house next month.
La nueva familia ocupará la casa el próximo mes.
C1 noun /ˈɒf.sprɪŋ/

offspring

descendencia
Meaning
a person's child or children; an animal's young
Example
The bird carefully fed its offspring.
El pájaro alimentó cuidadosamente a su descendencia.
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.
C2 noun /ˌɒpəˈrɛtə/

operetta

ópera ligera
Meaning
a short opera with light and humorous themes
Example
The theater staged a famous operetta by Gilbert and Sullivan.
El teatro presentó una famosa opereta de Gilbert y Sullivan.
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 adjective /ˌoʊvərˈbɛrɪŋ/

overbearing

opresivo
Meaning
unpleasantly or arrogantly domineering
Example
His overbearing attitude made everyone uncomfortable.
Su actitud opresiva hizo que todos se sintieran incómodos.
B2 noun /ɒpˈtɪʃən/

optician

optometrista
Meaning
A person who makes or sells glasses and contact lenses.
Example
The optician adjusted my new glasses to fit better.
El optometrista ajustó mis nuevas gafas para que quedaran mejor.
B2 adverb /əˈfɪʃəli/

officially

oficialmente
Meaning
in a formal or authorized way
Example
The building was officially opened by the mayor.
El edificio fue oficialmente inaugurado por el alcalde.
C2 adjective /əˈprəʊ.bri.əs/

opprobrious

despectivo
Meaning
Expressing strong criticism or scorn.
Example
He made opprobrious remarks about his opponent.
Él hizo comentarios despectivos sobre su oponente.
C1 adjective /aʊtˈmoʊdɪd/

outmoded

desfasado
Meaning
No longer in fashion or useful; outdated.
Example
That old computer is completely outmoded.
Esa computadora antigua está completamente desfasada.
B2 adjective ˌɒp.ərˈeɪ.ʃən.əl

operational

operativo
Meaning
In working order; ready for use.
Example
The space project will be operational by 2025.
El proyecto espacial estará operativo para 2025.
B2 adjective /əˈfen.sɪv/

Offensive

ofensivo; insultante; agresivo
Meaning
causing displeasure or resentment; insulting; aggressive
Example
His offensive remarks hurt everyone's feelings.
Sus comentarios ofensivos lastimaron los sentimientos de todos.
C1 adjective /ˈɔːrθədɑːks/

orthodox

ortodoxo
Meaning
conforming to traditional beliefs or practices
Example
He comes from a very orthodox family.
Él proviene de una familia muy ortodoxa.
B1 verb /ˈɒpəreɪt/

operate

operar
Meaning
to function; to control or manage; to perform surgery
Example
The surgeon will operate on the patient tomorrow.
El cirujano operará al paciente mañana.
C2 adjective /ˈɑːsɪˌfaɪd/

ossified

convertido en hueso, rígido
Meaning
Turned into bone or become rigid; unwilling to change.
Example
The company had an ossified management structure that resisted innovation.
La empresa tenía una estructura de gestión rígida que resistía la innovación.
A2 adjective /əˈlɪmpɪk/

olympic

olímpico
Meaning
related to the Olympic Games, a major international sporting event
Example
She trained hard to compete in the Olympic Games.
Ella entrenó duro para competir en los Juegos Olímpicos.
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 /ˈɒn.rʌʃ/

onrush

embestida
Meaning
A sudden powerful forward or downward rush or flow.
Example
The onrush of water swept away the bridge.
La embestida de agua arrastró el puente.
C2 adjective /əbˈstrɛpərəs/

obstreperous

ruidoso y difícil de controlar
Meaning
Noisy and difficult to control.
Example
The obstreperous students disrupted the class.
Los estudiantes ruidosos interrumpieron la clase.
C1 adverb /ˈɒp.tɪ.məl.i/

optimally

de manera óptima
Meaning
In the most effective or efficient way possible.
Example
Tasks should be allocated optimally for maximum output.
Las tareas deben asignarse de manera óptima para obtener el máximo rendimiento.
C2 noun /ˌɔːrdɪˈneɪʃən/

ordination

ordenación
Meaning
The ceremony of conferring holy orders or official religious authority.
Example
The church held a special service for the ordination of new priests.
La iglesia celebró un servicio especial para la ordenación de nuevos sacerdotes.
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 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 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.
C2 adjective /ˈɔːrnəri/

ornery

gruñón
Meaning
bad-tempered and combative; stubborn
Example
The ornery old man refused to leave his chair.
El gruñón anciano se negó a dejar su silla.
C2 noun /əbˈsɪdiən/

obsidian

obsidiana (roca volcánica oscura y vidriosa)
Meaning
A hard, dark, glasslike volcanic rock formed by rapid solidification of lava.
Example
The knife was made from sharp obsidian.
El cuchillo estaba hecho de obsidiana afilada.
C2 noun /əˈblɪkwɪti/

obliquity

oblicuidad
Meaning
Deviation from moral or usual conduct; indirectness or lack of straightforwardness.
Example
The politician was criticized for the obliquity of his answers.
El político fue criticado por la oblicuidad de sus respuestas.
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.
C1 noun /əbˈzɜːrvətɔːri/

observatory

observatorio
Meaning
A building equipped for observing astronomical or meteorological events.
Example
The observatory is open to the public on weekends.
El observatorio está abierto al público los fines de semana.
A1 adverb /wʌns/

Once

una vez; alguna vez en el pasado
Meaning
one time only; at some time in the past; formerly
Example
I have been to Paris once in my life.
He estado en París una vez en mi vida.
B2 verb /ˌoʊvərˈteɪk/

overtake

adelantar
Meaning
to catch up with and pass someone or something; to surpass
Example
The runner managed to overtake his competitor in the final lap.
El corredor logró adelantar a su competidor en la última vuelta.
B2 noun /ˈaʊtˌbreɪk/

outbreak

brote
Meaning
a sudden start or occurrence of something unpleasant, like disease or violence
Example
There was an outbreak of flu in the city.
Hubo un brote de gripe en la ciudad.
C1 adjective /ˈɔːrdɪnəl/

ordinal

ordinal
Meaning
Relating to the order or position of something in a sequence (first, second, third, etc.).
Example
The ordinal number 'third' indicates position in a sequence.
El número ordinal 'tercero' indica la posición en una secuencia.
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.
C2 noun /ˈɒbsɪkwiːz/

obsequies

ritos fúnebres
Meaning
Funeral rites or ceremonies.
Example
The obsequies for the late leader drew thousands of mourners.
Los ritos fúnebres para el líder fallecido atrajeron a miles de dolientes.
B2 noun /ɔːrˈɡæn.ɪk ˈfɑːr.mɪŋ/

organic farming

agricultura orgánica
Meaning
Farming method that avoids synthetic chemicals and fertilizers, using natural methods instead.
Example
Organic farming improves soil health and reduces pollution.
La agricultura orgánica mejora la salud del suelo y reduce la contaminación.
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 adjective /ˌəʊvərˈstɪmjʊˌleɪtɪd/

overstimulated

sobrestimulado
Meaning
Excessively excited or aroused, overwhelmed by too much stimulus.
Example
Overstimulated minds can lead to burnout and decreased productivity.
Las mentes sobrestimuladas pueden conducir al agotamiento y a una menor productividad.
C1 adjective /əˈblaɪdʒɪŋ/

obliging

servicial
Meaning
Willing to help or do favors; accommodating.
Example
The staff at the hotel were very obliging and friendly.
El personal del hotel era muy servicial y amable.
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.
B2 noun /ˈaʊt.laɪn/

Outline

esquema; contorno; resumen
Meaning
a general description or plan showing the essential features of something; the main points
Example
The teacher provided an outline of the course syllabus.
El maestro proporcionó un esquema del syllabus del curso.
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.
A2 noun /ˈʌv.ən/

Oven

horno
Meaning
an enclosed compartment used for heating, baking, or drying food
Example
She baked cookies in the oven for thirty minutes.
Ella horneó galletas en el horno durante treinta minutos.
B2 noun /ˈoʊvərpæs/

overpass

paso elevado
Meaning
A bridge that carries one road or railway over another.
Example
The new overpass reduced traffic congestion in the city.
El nuevo paso elevado redujo la congestión de tráfico en la ciudad.
B1 adverb /ˈʌðərwaɪz/

Otherwise

de otra manera; si no; o sino
Meaning
in a different way; if not; or else; apart from that
Example
Study hard, otherwise you will fail the exam.
Estudia mucho, de lo contrario, reprobarás el examen.
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.
A1 interjection /oʊ/

oh

¡Oh!
Meaning
used to express surprise, realization, or understanding
Example
Oh, I didn't know you were here!
¡Oh, no sabía que estabas aquí!
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.
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 /oʊˈbiː.di.əns/

Obedience

obediencia
Meaning
compliance with an order, request, or law; submission to authority
Example
Children should show obedience to their parents.
Los niños deben mostrar obediencia a sus padres.
C2 verb /ˈɑːbvieɪt/

obviate

eliminar
Meaning
To remove a need or difficulty; to prevent or avoid something.
Example
This new system obviates the need for manual data entry.
Este nuevo sistema elimina la necesidad de ingresar datos manualmente.
A1 noun /ɒkˈtoʊbər/

october

octubre
Meaning
the tenth month of the year in the Gregorian calendar
Example
The weather becomes cooler in October.
El clima se vuelve más fresco en octubre.
B2 noun /ˈɒt.ər/

Otter

nutria
Meaning
a mammal with webbed feet that lives near water and feeds on fish
Example
The playful otter swam gracefully in the river.
La nutria juguetona nadaba con gracia en el río.