B1 verb /əbˈzɜːrv/

observe

観察する

Meaning

to watch carefully; to notice or perceive something

Example

Scientists observe the behavior of animals in the wild.

科学者たちは野生動物の行動を観察します。

C1 verb /ˌaʊtˈduː/

outdo

超える

Meaning

To do better than someone else; to surpass.

Example

She always tries to outdo her classmates in exams.

彼女は試験でクラスメートを常に超えようとします。

B2 noun /ˈaʊtˌbreɪk/

outbreak

発生

Meaning

a sudden start or occurrence of something unpleasant, like disease or violence

Example

There was an outbreak of flu in the city.

街でインフルエンザが発生した。

C2 adjective /ˈɒsiəs/

osseous

骨のような

Meaning

consisting of or turned into bone; bony

Example

The fossil showed osseous structures of the ancient creature.

化石は古代の生物の骨のような構造を示しました。

C1 noun /oʊθ/

Oath

誓い

Meaning

a solemn promise or declaration; a sworn statement

Example

The doctor took an oath to help patients.

医師は患者を助けることを誓いました。

B2 noun /ˈɔːɡənɪzəm/

organism

生物

Meaning

a living thing that has an organized structure and can grow and reproduce

Example

Every organism needs water to survive.

すべての生物は生き残るために水を必要とします。

B1 noun /əˈpɪn.jən/

Opinion

意見

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.

私の意見では、これは最良の解決策です。

C2 noun /ˈɒn.rʌʃ/

onrush

突発的な流れ

Meaning

A sudden powerful forward or downward rush or flow.

Example

The onrush of water swept away the bridge.

水の突発的な流れが橋を流しました。

C2 noun /oʊliˈændər/

Oleander

オレアンダー

Meaning

a poisonous evergreen shrub with clusters of white, pink, or red flowers

Example

The beautiful oleander flowers bloomed in the garden despite their toxic nature.

美しいオレアンダーの花が庭で咲いていましたが、その毒性に関わらず。

B2 noun /ˈoʊ.vər ɡroʊθ/

Over growth

過剰成長

Meaning

excessive growth beyond normal size; too much development or expansion

Example

The overgrowth of weeds made the garden look untidy.

雑草の過剰な繁茂が庭を乱雑に見せた。

A2 noun /ˈɒbdʒɪkt/

object

物体

Meaning

a thing that can be seen and touched

Example

The table is an object in the room.

テーブルは部屋の中の物体です。

B2 noun /ˈoʊvərpæs/

overpass

高架橋

Meaning

A bridge that carries one road or railway over another.

Example

The new overpass reduced traffic congestion in the city.

新しい高架橋は市内の交通渋滞を減らしました。

C2 noun /ˈɒbsɪkwiːz/

obsequies

葬儀儀式

Meaning

Funeral rites or ceremonies.

Example

The obsequies for the late leader drew thousands of mourners.

故リーダーの葬儀儀式には、数千人の弔問客が集まりました。

C2 verb /oʊˈpaɪn/

opine

意見を述べる

Meaning

to express an opinion or belief

Example

The professor opined that the policy would fail.

教授はその政策が失敗するだろうと述べました。

B2 noun /ɒdz/

odds

確率

Meaning

the likelihood or probability of something happening; chances for or against something

Example

The odds of winning the lottery are very low.

宝くじに当選する確率は非常に低いです。

B2 adjective + noun ˈɒptɪməl ˈtempərətʃər

optimal temperature

最適温度

Meaning

The best or most favorable temperature for a particular purpose

Example

Winter provides optimal temperature for farming.

冬は農業に最適な温度を提供します。

A2 noun /ˈɒpərə/

opera

オペラ

Meaning

a dramatic performance in which the actors sing most of their lines

Example

We watched a beautiful opera at the theater last night.

昨晩、劇場で美しいオペラを観ました。

B2 noun /ˈɔːrɡənaɪzər/

organizer

主催者

Meaning

a person who arranges or coordinates activities, events, or groups; a tool or item used to keep things in order

Example

She worked as the main organizer of the international conference.

彼女は国際会議の主要な主催者だった。

C1 noun/verb /ˈoʊvərˌhæŋ/

overhang

突出部

Meaning

To extend outward and hang over something; a projecting part.

Example

The roof overhang provides shade in the summer.

屋根のオーバーハングは夏に日陰を提供します。

C1 verb /ˌaʊtˈweɪ/

outweigh

より重要である

Meaning

To be more important, valuable, or significant than something else.

Example

The benefits of the new policy outweigh the risks.

新しい政策の利益はリスクを上回っています。

C2 noun /ɔːrˈθɑːɡrəfi/

orthography

正書法

Meaning

The conventional spelling system of a language.

Example

English orthography can be confusing for learners.

英語の正書法は学習者にとって混乱を招くことがあります。

B2 adjective /ˌfæʃ.ənd/

Outdated

時代遅れ

Meaning

obsolete; no longer current

Example

This computer software is completely outdated.

このソフトウェアは完全に時代遅れです。

B1 verb /ˈɒpəreɪtɪŋ/

operating

運営する

Meaning

to control or manage the functioning of something

Example

The company has been operating in this market for five years.

その会社はこの市場で5年間運営されています。

C2 noun /ˈɔːrɪndʒfɪn ˈleɪbiːoʊ/

Orangefin labeo

オレンジフィンラベオ

Meaning

a freshwater fish species native to South Asian rivers, commonly found in Bangladesh and India

Example

The orangefin labeo is an important food fish in Bangladesh.

オレンジフィンラベオはバングラデシュで重要な食用魚です。

C1 noun /ˈəʊ.nəs/

onus

責任

Meaning

A duty or responsibility, especially a heavy one.

Example

The onus is on the government to provide relief to the victims.

犠牲者に支援を提供する責任は政府にあります。

C2 verb /ˌaʊtməˈnuːvər/

outmaneuver

巧妙に出し抜く

Meaning

to gain an advantage over an opponent by skillful or clever action

Example

The smaller company managed to outmaneuver its larger rival.

小さな会社は大きな競争相手を巧妙に出し抜くことに成功した。

C1 noun /oʊˈmɪʃ.ən/

Omission

省略; 除外

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.

リストから彼の名前を省略することは意図的でした。

A2 adjective /ˈɒb.vi.əs/

Obvious

明白な; 簡単に理解できる

Meaning

easily perceived or understood; clear and apparent to the mind

Example

It was obvious that she was upset about something.

それは彼女が何かについて不満を抱えていることが明らかでした。

C2 adjective /ˈɔːrəˌtʌnd/

orotund

豊かで明確な声

Meaning

full, rich, and clear in sound; pompous in style

Example

The actor's orotund voice filled the theater.

俳優の豊かな声が劇場に響き渡った。

B1 noun /ˈɑp.ʃən/

Option

オプション

Meaning

a thing that is or may be chosen; an alternative course of action

Example

You have the option to work from home or office.

自宅またはオフィスから仕事をするオプションがあります。

C1 adjective /ˌoʊvərˈbloʊn/

overblown

誇張された

Meaning

excessively exaggerated or inflated

Example

The controversy was overblown by the media.

メディアによって論争は誇張されました。

B2 noun /ˌɒpəˈzɪʃən/

opposition

反対

Meaning

the action of opposing or resisting something

Example

The opposition to the new law was strong.

新しい法律に対する反対は強かった。

A2 noun /ˈʌv.ən/

Oven

オーブン

Meaning

an enclosed compartment used for heating, baking, or drying food

Example

She baked cookies in the oven for thirty minutes.

彼女はオーブンで三十分間クッキーを焼きました。

C2 noun /əˈprəʊ.bri.əm/

opprobrium

非難, 恥辱

Meaning

Harsh criticism or public disgrace.

Example

The scandal brought opprobrium on the politician.

スキャンダルは政治家に非難を浴びせた。

C2 verb /əbˈvɜːrt/

obvert

反転する

Meaning

To turn something so as to face in a different direction; in logic, to convert a proposition by negating both subject and predicate.

Example

The teacher asked the students to obvert the statement for practice.

先生は生徒たちに練習のためにその声明をオブバートするように頼みました。

B1 noun /ˈɔr.ə.ʒɪn/

Origin

起源

Meaning

the point or place where something begins, arises, or is derived; the source

Example

Scientists are studying the origin of the universe.

科学者たちは宇宙の起源を研究しています。

B2 noun /wʌn θɜːd/

one-third

三分の一

Meaning

one part of something that is divided into three equal parts

Example

One-third of the class was absent today.

クラスの三分の一が今日は欠席でした。

B2 verb /oʊˈmɪt/

omit

省略する

Meaning

to leave out or exclude; to fail to include something

Example

Please don't omit any important details from your report.

レポートから重要な詳細を省略しないでください。

C2 noun /ˈɒrɪz(ə)n/

orison

祈り

Meaning

a prayer, especially a devout or formal one

Example

He whispered a quiet orison before going to sleep.

寝る前に静かな祈りをささやいた。

C1 noun /ˈoʊvərˌsiːər/

overseer

監督者

Meaning

a person who supervises work or workers; a manager

Example

The overseer made sure the workers followed safety rules.

監督者は、労働者が安全規則を守っていることを確認しました。

C1 adjective /ˈɔːrdɪnəl/

ordinal

順序数

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.

'第三'の順序数は、順番での位置を示します。

B2 noun /ˌɒb.zəˈveɪ.ʃənz/

observations

観察

Meaning

The action or process of observing something carefully.

Example

Observations of distant galaxies provide new insights.

遠くの銀河の観察は新たな洞察を提供します。

B2 verb /əˈrɪdʒɪneɪt/

originate

起源する

Meaning

to come into existence; to begin; to create or produce

Example

The tradition originated in ancient times.

その伝統は古代の時代に起源を持っています。

C1 adjective /ɔːˈneɪt/

ornate

華やかな

Meaning

elaborately or highly decorated

Example

The palace hall was filled with ornate furniture and paintings.

宮殿のホールは華やかな家具と絵画でいっぱいだった。

A2 noun /ˈʌn.jən/

Onion

玉ねぎ

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.

カレーのレシピのためにいくつか玉ねぎを切る必要があります。

C1 noun /ˈɑd.ɪ.ti/

Oddity

珍奇な現象

Meaning

something that is strange or unusual; a peculiar trait

Example

His habit of sleeping standing up was considered an oddity.

彼の立って寝る習慣は珍奇な現象と見なされていました。

C1 adjective /ˌɒmnɪˈprezənt/

omnipresent

至る所に存在する

Meaning

(of God) present everywhere at the same time.

Example

Social media has become an omnipresent force in modern society.

ソーシャルメディアは現代社会において至る所に存在する力となりました。

C1 adjective /ˌɔː.riˈen.təl/

Oriental

東アジアの国々に関連する; 東方

Meaning

relating to the countries of East Asia; eastern

Example

The museum has a beautiful collection of oriental art.

博物館には美しいオリエンタルアートのコレクションがあります。

B2 adjective /ˌɑːp.təˈmɪs.tɪk/

optimistic

楽観的

Meaning

hopeful and confident about the future

Example

She is optimistic about the success of her new project.

彼女は新しいプロジェクトの成功に楽観的です。

B2 noun ˈəʊnəʃɪp

ownership

所有権

Meaning

The act, state, or right of possessing something; legal title to something.

Example

Ownership of resources was crucial.

資源の所有権は重要でした。

B2 noun /oʊˈbiː.di.əns/

Obedience

服従

Meaning

compliance with an order, request, or law; submission to authority

Example

Children should show obedience to their parents.

子供たちは両親に従うべきです。

C2 noun ˈɒpjʊləns

opulence

富裕

Meaning

Great wealth or luxuriousness.

Example

The opulence of the mansion was evident in its ornate furnishings.

豪邸の富裕さはその華やかな家具に明らかでした。

B1 adjective /əˈkeɪ.ʒən.əl/

Occasional

偶然の

Meaning

occurring infrequently or irregularly; happening from time to time

Example

She enjoys occasional walks in the park.

彼女は公園で偶然の散歩を楽しんでいます。

B2 adjective /ˈɒp.ʃən.əl/

Optional

任意

Meaning

not compulsory; left to choice

Example

Wearing a tie is optional for this event.

このイベントではネクタイの着用は任意です。

A1 adjective /oʊld/

old

古い

Meaning

having lived for a long time; not new or young

Example

He still drives his old car.

彼は今でも古い車を運転しています。

C2 noun /ˌɒn.əˌmæt.əˈpiː.ə/

onomatopoeia

オノマトペ

Meaning

The formation of a word from a sound associated with what is named.

Example

The word 'buzz' is an example of onomatopoeia.

'バズ'という言葉はオノマトペの一例です。

C2 noun ˌɒbfəsˈkeɪʃən

obfuscation

難解化, 混乱

Meaning

The action of making something obscure, unclear, or unintelligible.

Example

The obfuscation of the data made it difficult to interpret.

データの難解化により、解釈が困難になりました。

C1 noun /ˌəʊvərɪksˌplɔɪˈteɪʃən/

overexploitation

過剰搾取

Meaning

The unsustainable use of natural resources at a rate that exceeds their ability to regenerate, leading to depletion and environmental degradation.

Example

Overexploitation of natural resources leads to environmental degradation.

自然資源の過剰搾取は環境の悪化を引き起こします。

C2 noun /ˌoʊpəˈlɛsəns/

opalescence

オパレスセンス

Meaning

a milky or pearly appearance of a surface like that of an opal

Example

The pearl had a gentle opalescence under the light.

パールは光の下で優しいオパレスセンスを持っていました。

C1 noun /ˈɒf.sprɪŋ/

offspring

子孫

Meaning

a person's child or children; an animal's young

Example

The bird carefully fed its offspring.

その鳥は注意深く自分の子孫に餌を与えました。

B1 adverb /əˈrɪdʒɪnəli/

originally

元々

Meaning

in the beginning, at first

Example

Originally, she wanted to be a doctor.

元々、彼女は医者になりたかった。

C1 adjective əʊˈpeɪk

opaque

不透明, 理解しにくい

Meaning

Not able to be seen through; not transparent; difficult to understand.

Example

The glass was too opaque to see through.

そのガラスは不透明すぎて、透けて見えませんでした。

B2 noun /əbˈsɛʃən/

obsession

執着

Meaning

An idea, thought, or concern that continually preoccupies or intrudes on a person's mind.

Example

His obsession with success drove him to work day and night.

成功への執着が彼を昼夜働かせた。

C1 adjective /ˌaʊtˈlændɪʃ/

outlandish

奇妙

Meaning

Looking or sounding bizarre or unfamiliar; strange.

Example

He wore an outlandish costume to the festival.

彼は祭りに奇妙な衣装を着ていました。

B2 noun /ˈɔːrnəmənt/

ornament

装飾品

Meaning

A decorative object that adds beauty to something.

Example

The Christmas tree was decorated with colorful ornaments.

クリスマスツリーはカラフルな装飾品で飾られていました。

C2 adjective /ˌɔːfˈkiː/

off-key

外れた音

Meaning

out of tune; not in accordance with expected standards

Example

The singer was slightly off-key during the performance.

歌手はパフォーマンス中に少し外れた音だった。

C1 verb /aʊtˈwɪt/

outwit

巧妙に出し抜く

Meaning

to defeat or gain an advantage over someone by being more clever or cunning

Example

The fox managed to outwit the hunters.

キツネは猟師たちを出し抜くことができました。

C1 adjective /ɒmˈnɪv.ər.əs/

Omnivorous

雑食性

Meaning

eating both plants and animals; feeding on various kinds of food

Example

Bears are omnivorous animals that eat both plants and meat.

クマは雑食性の動物で、植物と肉を食べます。

B2 noun /ˈaʊtɪŋ/

outing

お出かけ

Meaning

a short trip or excursion, often for leisure or enjoyment

Example

They had a lovely outing at the beach last weekend.

彼らは先週末、ビーチで素晴らしいお出かけをしました。

C1 noun /ˌɑːk.sɪˈmɔːr.ɒn/

oxymoron

オキシモロン

Meaning

a figure of speech where two contradictory terms are combined

Example

The phrase 'deafening silence' is a classic oxymoron.

「耳をつんざくような静けさ」というフレーズは、典型的なオキシモロンです。

B2 adjective /əˈfen.sɪv/

Offensive

攻撃的な; 侮辱的な; 攻撃的

Meaning

causing displeasure or resentment; insulting; aggressive

Example

His offensive remarks hurt everyone's feelings.

彼の攻撃的な発言は、全員の気持ちを傷つけました。

C2 noun /ˌɒpəˈrɛtə/

operetta

軽いオペラ

Meaning

a short opera with light and humorous themes

Example

The theater staged a famous operetta by Gilbert and Sullivan.

劇場はギルバートとサリヴァンの有名な軽いオペラを上演しました。

B2 noun/verb /ˈoʊvərˌdoʊs/

overdose

過剰摂取

Meaning

An excessive and dangerous amount of a drug; to take too much of a substance.

Example

He was rushed to the hospital after a drug overdose.

薬物の過剰摂取で病院に運ばれました。

B2 adverb /ˈoʊpənli/

Openly

率直に; 公然と

Meaning

in a frank and honest way; without concealment; publicly

Example

She spoke openly about her struggles with mental health.

彼女はメンタルヘルスの問題についてオープンに話した。

B2 adverb /ˈaʊtraɪt/

Outright

直接に; 完全に; ためらわずに

Meaning

completely; directly; without reservation or concealment

Example

She rejected the proposal outright.

彼女はその提案を直接拒否した。

A2 adjective /ˈɑp.ə.zɪt/

Opposite

反対の; 完全に異なる; 向かい合っている; 逆の;

Meaning

Contrary; completely different; facing each other; reverse;

Example

They have opposite views on politics but remain good friends.

彼らは政治に関して対立した見解を持っていますが、良い友達のままです。

C1 noun /ˈɒptɪks/

optics

光学

Meaning

The branch of physics dealing with light and vision.

Example

She studied optics to understand how lenses work.

彼女はレンズがどのように機能するかを理解するために光学を学びました。

B2 noun /ˈɒkjʊpənt/

occupant

乗客

Meaning

A person who resides in or is present in a house, vehicle, seat, or place.

Example

The car had three occupants at the time of the accident.

事故の時、車には三人の乗客がいました。

B2 noun /əbˈzɜːvər/

observer

観察者

Meaning

a person who watches or notices something

Example

The observer took notes during the meeting.

観察者は会議中にメモを取った。

C1 noun /əbˈzɜːvəns/

observance

遵守

Meaning

The practice of following a custom, rule, or religious law.

Example

The festival is held in observance of a centuries-old tradition.

その祭りは、数世代にわたる伝統を遵守して行われます。

C1 adjective /əˈkʌlt/

occult

オカルト

Meaning

Relating to mysterious, supernatural, or magical powers and practices.

Example

She had always been fascinated by the occult and its hidden knowledge.

彼女は常にオカルトとその隠された知識に魅了されていた。

C1 adjective ˈɒptɪmaɪzd

optimized

最適化, 改善, より効率的

Meaning

Made as fully perfect, functional, or effective as possible; improved to achieve maximum efficiency.

Example

The system has been optimized for faster performance.

システムはより速いパフォーマンスのために最適化されました。

A2 verb /ˈɔːfər/

offer

申し出る

Meaning

to present something for acceptance or rejection; to propose

Example

She offered to help with the project.

彼女はプロジェクトを手伝うと申し出た。

B2 noun /ɒpˈtɪʃən/

optician

眼鏡技師

Meaning

A person who makes or sells glasses and contact lenses.

Example

The optician adjusted my new glasses to fit better.

オプティシャンは私の新しい眼鏡をより良くフィットするように調整しました。

C1 noun /oʊˈeɪ.sɪs/

Oasis

オアシス

Meaning

a fertile spot in a desert where water is found; a pleasant refuge

Example

The travelers found an oasis after days in the desert.

旅行者たちは砂漠で数日後にオアシスを見つけました。

B2 adjective /ˈɔː.də.li/

Orderly

整然とした; 系統的な; 平和的な

Meaning

well-organized; systematic; peaceful

Example

Please keep your desk orderly and clean.

デスクを整然とした状態できれいに保ってください。

C1 noun /ˈɔːrkɪd/

Orchid

オーキッド

Meaning

a diverse family of flowering plants known for their exotic and often fragrant flowers

Example

The white orchid on the windowsill bloomed for months.

窓辺の白いオーキッドは何ヶ月も咲き続けました。

C2 adjective /ɒmˈnɪp.ə.tənt/

omnipotent

全能

Meaning

Having unlimited power; able to do anything; all-powerful.

Example

In many religions, God is considered omnipotent.

多くの宗教では、神は全能だと考えられています。

C1 adjective /ˈəʊnərəs/

onerous

重い

Meaning

involving a great deal of effort, difficulty, or burden

Example

Fulfilling the contract proved to be an onerous task for the company.

契約を履行することは会社にとって負担の大きい仕事だと証明された。

B2 noun /ˈɑp.tə.mɪst/

Optimist

楽観主義者

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.

楽観主義者として、彼女は常に物事が改善されると信じていました。

C1 noun /ˈɔr.i.ənt/

Orient

東洋、特に東アジアの国々

Meaning

the East, especially countries of eastern Asia; to determine one's position or direction

Example

Many spices come from the Orient.

多くの香辛料がオリエントから来ています。

B2 adjective; verb (past participle) /ˈɒkjʊpaɪd/

occupied

使用中の；占領された

Meaning

being in use or taken; filled or lived in; controlled or held by force

Example

The room is occupied, so please wait outside.

その部屋は使用中なので、外で待ってください。

B2 noun /əˌrɪʒ.əˈnæl.ə.ti/

Originality

独創性

Meaning

the quality of being novel or unusual; the ability to think independently and creatively

Example

The artist's work showed great originality and creativity.

アーティストの作品は大きな独創性と創造性を示した。

B1 noun /ˈɑb.stə.kəl/

Obstacle

障害物

Meaning

something that blocks or makes progress difficult; a barrier

Example

Bad weather was the main obstacle to our journey.

悪天候が私たちの旅行の最大の障害物でした。

A1 adjective/adverb /ˈoʊnli/

only

唯一

Meaning

without others; solely

Example

He is the only person who knows the secret.

彼はその秘密を知っている唯一の人です。

C1 adverb /ˈɒp.tɪ.məl.i/

optimally

最適に

Meaning

In the most effective or efficient way possible.

Example

Tasks should be allocated optimally for maximum output.

タスクは最大の成果を上げるために最適に割り当てるべきです。

C2 noun /ˈəʊpəs/

opus

創作作品

Meaning

A creative work, especially a large and important piece of music or art.

Example

The composer considered the symphony his greatest opus.

作曲家は交響曲を自分の最も偉大な創作作品と見なしていました。

C2 noun (plural) /ˈɔːrdʒiːz/

orgies

オルギー

Meaning

Wild gatherings involving excessive indulgence in food, drink, or sexual activity.

Example

The ancient Romans were infamous for their lavish feasts and orgies.

古代ローマ人は豪華な宴会とオルギーで悪名高かった。

C2 noun /ɒkˈteɪvoʊ/

octavo

オクターヴォ (紙を8つに折りたたんで作られた本のサイズ)

Meaning

A size of book page resulting from folding a sheet of paper into eight leaves (sixteen pages).

Example

The old library contained rare octavo editions of Shakespeare.

古い図書館にはシェイクスピアの珍しいオクターヴォ版がありました。

B2 noun /ˈɒt.ər/

Otter

カワウソ

Meaning

a mammal with webbed feet that lives near water and feeds on fish

Example

The playful otter swam gracefully in the river.

遊び好きなカワウソは川で優雅に泳いでいました。

C1 adjective /ˌaʊt ən ˈaʊt/

out-and-out

完全な

Meaning

complete; absolute; used to emphasize something extreme

Example

The speech was an out-and-out lie.

そのスピーチは完全な嘘だった。

C1 verb /ˌoʊvərˈrʌn/

overrun

侵略する

Meaning

to spread over or occupy completely; to exceed a limit or time

Example

The garden was overrun with weeds.

庭は雑草に覆われていた。

侮辱する

Meaning

to cause displeasure or resentment; to hurt someone's feelings

Example

His rude comments offended many people at the meeting.

彼の無礼なコメントは会議で多くの人々を怒らせました。