ostracism
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C1 noun /ˈɒstrəsɪzəm/

ostracism

追放
Meaning
The act of excluding someone from a group or society.
Example
The student faced ostracism after breaking the rules.
その学生は規則を破った後、追放に直面しました。
C1 noun /ˌɑːpərˈtuːnɪst/

opportunist

機会主義者
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.
彼は常に自分の利益を第一に考える機会主義者として見られています。
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。
C1 noun /ˌɑːsɪˈleɪʃən/

oscillation

振動
Meaning
The movement back and forth at a regular speed.
Example
The oscillation of the pendulum controls the clock.
振り子の振動が時計を制御します。
C1 noun /əbˈstrʌkʃən/

obstruction

障害
Meaning
Something that blocks or gets in the way; the action of obstructing.
Example
There was an obstruction on the railway track.
鉄道の線路に障害がありました。
C1 adjective /ˌəʊ.vərˈɑː.tʃɪŋ/

overarching

全体的な, 包括的な, 包み込む
Meaning
Comprehensive or all-embracing; forming an arch over something.
Example
The overarching theme of the book is human resilience.
その本の大きなテーマは人間の回復力です。
C1 noun /ˈɔɪntmənt/

ointment

軟膏
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.
医師は彼の腕のやけどのために軟膏を処方しました。
C1 verb /aʊtˈlɪv/

outlive

より長生きする
Meaning
to live longer than someone or something else
Example
She outlived all her siblings.
彼女はすべての兄弟姉妹より長生きしました。
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。
C1 verb /ˈɒs.ɪ.leɪt/

oscillate

二つの点または状態の間で前後に動くまたは揺れる
Meaning
To swing or move back and forth between two points or states
Example
The stock market tends to oscillate during uncertain times.
株式市場は不確実な時期に振動しがちです。
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 noun /ˈɔr.ə.kəl/

Oracle

オラクル
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.
古代ギリシャ人はデルポイのオラクルに相談しました。
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。
C1 verb əˈblɪt.ə.reɪt

obliterate

完全に破壊する
Meaning
To destroy utterly; wipe out completely, to erase or remove something completely.
Example
The storm obliterated entire villages.
嵐は村全体を完全に破壊しました。
C1 adjective ˈɒb.stɪ.nət

obstinate

頑固
Meaning
Refusing to change one's mind or accept others' advice easily.
Example
He remained obstinate despite the logical arguments.
彼は論理的な議論にもかかわらず頑固なままでいた。
C1 noun /oʊˈveɪʃən/

ovation

拍手
Meaning
an enthusiastic show of approval, especially by clapping hands
Example
The actor received a standing ovation after his performance.
俳優はパフォーマンス後にスタンディングオベーションを受けました。
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。
C1 adjective /ˌɔːrθəˈpiːdɪk/

orthopedic

骨や筋肉の変形の修正に関連する
Meaning
Relating to the correction of deformities of bones or muscles.
Example
She visited an orthopedic surgeon for her back pain.
彼女は背中の痛みのために整形外科医に行った。
C1 noun /ˌɒk.sɪ.dʒɪˈneɪ.ʃən/

oxygenation

酸素供給または治療
Meaning
The process of supplying or treating with oxygen.
Example
Deep breathing exercises improve oxygenation of the body.
深呼吸の練習は身体の酸素供給を改善します。
C1 verb /ˈɒp.tɪ.maɪz/

optimize

最適化する
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.
会社はサプライチェーンの最適化に取り組んでいます。
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。
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。
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。
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。
C1 noun /ˌoʊvərprəˈdʌkʃən/

overproduction

過剰生産
Meaning
The act of producing more of something than is needed or can be consumed.
Example
The economic crisis was caused by the overproduction of goods.
経済危機は商品の過剰生産によって引き起こされた。
C1 noun /əˈpreʃ.ən/

Oppression

抑圧; 虐待; 圧政;
Meaning
cruel or unjust treatment or exercise of authority; the state of being subject to harsh treatment
Example
The people fought against political oppression.
人々は政治的な抑圧に反対して戦った。
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。
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。
C1 adjective /ˌoʊvərˈrɔt/

overwrought

興奮した / 過度に緊張した
Meaning
extremely agitated or nervous; excessively elaborate
Example
She was too overwrought to speak clearly after the accident.
事故後、彼女は興奮しすぎて、はっきりと話すことができなかった。
C1 noun /əbˈzɜːrvətɔːri/

observatory

天文台
Meaning
A building equipped for observing astronomical or meteorological events.
Example
The observatory is open to the public on weekends.
天文台は週末に一般公開されています。
C1 adjective /əbˈzɜːrvənt/

Observant

観察力のある
Meaning
quick to notice things; watchful; attentive
Example
The observant detective noticed every small detail at the crime scene.
観察力のある探偵は犯罪現場のあらゆる小さな詳細に気づきました。
C1 noun /ˈoʊ.vər spɪl/

Over-spill

オーバーフロー
Meaning
the overflow of liquid from a container; excess that cannot be contained
Example
The overspill from the river flooded nearby farms.
川の溢れが近くの農場を水浸しにした。
C1 noun ˈaʊt.sɔːr.sɪŋ

outsourcing

アウトソーシング
Meaning
The practice of having certain job functions done outside a company instead of having an in-house department or employee handle them.
Example
Many companies use outsourcing to reduce labor costs.
多くの企業はコスト削減のためにアウトソーシングを利用しています。
C1 adjective /ˌɒstɛnˈteɪʃəs/

ostentatious

見せびらかしの
Meaning
Characterized by a showy or pretentious display intended to impress others.
Example
He wore an ostentatious gold chain to the party.
彼はパーティーで見せびらかしの金のチェーンをしていました。
C1 noun /ˈaʊtriːtʃ/

outreach

支援拡大
Meaning
The act of providing services or support to people who might not otherwise have access to them.
Example
The charity launched a new outreach program for the homeless.
チャリティはホームレスのために新しい支援拡大プログラムを開始しました。
C1 adjective /ˈɒptɪk/

optic

視覚の
Meaning
Relating to the eye or vision.
Example
The optic nerve carries signals from the eye to the brain.
視神経は目から脳に信号を伝達します。
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 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。
C1 noun ˌɒk.sɪˈdeɪ.ʃən

oxidation

酸化
Meaning
A chemical reaction that involves the combination of a substance with oxygen, often causing deterioration.
Example
Oxidation causes metal surfaces to weaken.
酸化は金属表面を弱めます。
C1 noun əˈblɪv.i.ən

oblivion

忘却, 破壊, 消失
Meaning
The state of being unaware or unconscious of what is happening; complete forgetfulness.
Example
His name faded into oblivion over time.
彼の名前は時と共に忘却の中に消えた。
C1 noun /ˈɑːdəsi/

odyssey

長い旅
Meaning
a long, adventurous journey; a series of experiences
Example
Her career has been an odyssey of challenges and achievements.
彼女のキャリアは挑戦と成果の長い旅でした。
C1 adjective əˈblɪv.i.əs

oblivious

無自覚
Meaning
Being completely unaware of surrounding events.
Example
He was oblivious to the noise around him while reading.
彼は読書中に周りの騒音に全く無自覚だった。
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 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 noun /ˈoʊvərˌtoʊn/

overtone

微妙な意味
Meaning
A subtle quality, implication, or additional meaning beyond the obvious.
Example
His speech had political overtones that were hard to ignore.
彼のスピーチには無視できない政治的なニュアンスが含まれていました。
C1 verb /aʊst/

oust

追放する
Meaning
To remove someone from a position or place of power or authority.
Example
The rebels ousted the dictator from power.
反乱者は独裁者を権力から追い出しました。
C1 noun /ˈɒfʃuːt/

offshoot

分岐
Meaning
A branch or result that develops from something larger or more important.
Example
The startup was an offshoot of a major tech company.
そのスタートアップは大手テクノロジー企業からの分岐でした。
C1 adjective /əˈbliːk/

Oblique

斜め; 対角線; 間接的または回避的
Meaning
slanting; diagonal; indirect or evasive
Example
The artist drew an oblique line across the canvas.
アーティストはキャンバスに斜めの線を描いた。
C1 adjective /əbˈdʒek.ʃən.ə.bəl/

Objectionable

不快な
Meaning
arousing distaste or opposition; unpleasant or offensive
Example
His objectionable behavior made everyone uncomfortable.
彼の不快な行動は、皆を不快にさせた。
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。
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。
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。
C1 adjective /oʊˈvɜːrt/

overt

公然
Meaning
Done or shown openly; not hidden or secret.
Example
There was an overt display of hostility between the rivals.
ライバルの間に公然とした敵意の表れがあった。
C1 verb /ˌoʊvərˈpaʊər/

overpower

圧倒する
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.
兵士たちは敵軍を圧倒することができました。
C1 noun /ˈɒktɪv/

octave

Meaning
A series of eight musical notes, or the interval between one musical pitch and another with double its frequency.
Example
The singer's voice could easily reach the higher octave.
C1 verb /ɔːrˈdeɪn/

ordain

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.
C1 adjective /ˈɒptɪməm/

optimum

最適
Meaning
Most conducive to a favorable outcome; best.
Example
To achieve optimum results, we need to improve efficiency.
最適な結果を得るためには、効率を改善する必要があります。
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。
C1 verb /ˌoʊvərˈʃædoʊ/

overshadow

覆い隠す
Meaning
to appear more important or significant than something else, reducing its impact
Example
The scandal overshadowed his achievements.
スキャンダルは彼の業績を影にしました。
C1 adjective /ˌoʊvərˈbɛrɪŋ/

overbearing

押しつけがましい
Meaning
unpleasantly or arrogantly domineering
Example
His overbearing attitude made everyone uncomfortable.
彼の押しつけがましい態度は、みんなを不快にさせた。
C1 noun /ˈaʊtˌɡroʊθ/

outgrowth

成長
Meaning
something that grows out of something else; a natural development or result
Example
The new policy was an outgrowth of years of debate.
新しい政策は数年の議論の成長でした。
C1 noun ˌɒp.tɪ.maɪˈzeɪ.ʃən

optimization

最適化
Meaning
Improving processes to increase performance and efficiency.
Example
SEO optimization helps websites rank higher on search engines.
SEO最適化はウェブサイトが検索エンジンでより高いランクを獲得するのを助けます。
C1 adjective /ˌaʊtˈspoʊkən/

Outspoken

率直
Meaning
frank; speaking directly
Example
She is known for being outspoken about social issues.
彼女は社会問題について率直に話すことで知られています。
C1 noun /ˈɑn.set/

Onset

開始; 始まり
Meaning
the beginning or early stages of something; the start of a medical condition
Example
The onset of winter brought heavy snowfall.
冬の開始は大雪をもたらしました。
C1 adjective /ˈɔːrθədɑːks/

orthodox

Meaning
conforming to traditional beliefs or practices
Example
He comes from a very orthodox family.
C1 adjective /oʊˈbiːs/

obese

肥満
Meaning
Extremely overweight; having an excessive amount of body fat.
Example
The doctor advised the obese patient to adopt a healthier lifestyle.
医者は肥満患者に健康的な生活様式を採用するように勧めました。
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 noun /əˈkɜr.əns/

Occurrence

出来事
Meaning
an instance or event of something happening; the fact of occurring
Example
The occurrence of earthquakes is common in this region.
この地域では地震の出来事が一般的です。
C1 verb /əbˈsɛs/

obsess

Meaning
To preoccupy or fill the mind of someone continually and to an excessive degree.
Example
She tends to obsess over small details.
C1 noun /ˈɔːrθədɑːksi/

orthodoxy

正統
Meaning
traditional or generally accepted beliefs and practices
Example
The religious leader defended the orthodoxy of the faith.
宗教指導者は信仰の正統性を守った。
C1 verb /aʊtˈlæst/

outlast

他より長く続く
Meaning
to continue longer than; to endure beyond someone or something else
Example
The old castle has outlasted many generations.
その古い城は多くの世代を超えて生き残りました。
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。
C1 verb /uːz/

ooze

にじみ出る
Meaning
to slowly flow or leak out through small openings or pores
Example
Blood began to ooze from the small cut.
血が小さな切り傷からにじみ出た。
C1 verb /ˈɒfsɛt/

offset

相殺
Meaning
To counterbalance or compensate for something.
Example
The company's losses were offset by gains in other departments.
会社の損失は他の部門での利益で相殺されました。
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。
C1 adjective /əbˈstrʌk.tɪv/

Obstructive

妨害的な
Meaning
deliberately creating difficulties or preventing progress; hindering or blocking something
Example
The obstructive policies hindered economic growth.
妨害的な政策は経済成長を阻害した。
C1 adjective /ˈɒm.ɪ.nəs/

Ominous

不吉な; 脅威の
Meaning
giving the impression that something bad will happen; threatening; foreboding
Example
The dark clouds looked ominous before the storm.
嵐の前に、暗い雲は不吉に見えました。
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。
C1 noun /ˈɒktəɡən/

octagon

八角形
Meaning
A polygon with eight sides and eight angles.
Example
The stop sign is shaped like an octagon.
ストップサインは八角形をしています。
C1 adjective /əˈprɛs.ɪv/

Oppressive

抑圧的
Meaning
Harsh and authoritarian; overwhelming; causing distress; tyrannical;
Example
The oppressive heat made it difficult to work outside during the summer.
厳しい暑さは夏の間外で働くのを難しくした。
C1 adjective /ˌaʊt əv ðə ˈweɪ/

out-of-the-way

人里離れた場所
Meaning
remote or unusual; not in a convenient or usual location
Example
They stayed in an out-of-the-way village.
彼らは人里離れた村に滞在しました。
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。
C1 noun /ɒpˈtɒmətri/

optometry

視力検査学
Meaning
The practice or profession of examining the eyes and prescribing corrective lenses.
Example
She studied optometry at the university to become an eye specialist.
彼女は大学でオプトメトリーを学び、眼科専門医になりました。
C1 noun /ˈɑːlɪˌɡɑːrki/

oligarchy

寡頭政治
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.
その国は裕福なオリガーキーによって支配され、すべての資源を支配していました。
C1 verb ˈɔː.kɪ.streɪ.tɪd

orchestrated

精巧に組織された
Meaning
Planned or coordinated carefully and deliberately.
Example
The attacks were orchestrated with precision.
攻撃は正確に組織されていた。
C1 noun /ˈɔr.ə.tər/

Orator

演説家
Meaning
a public speaker, especially one who is eloquent or skilled in speaking
Example
The famous orator delivered an inspiring speech.
有名な演説家が感動的なスピーチを行った。
C1 noun ˌɒb.səˈlɛs.əns

obsolescence

陳腐化
Meaning
The process of becoming obsolete or outdated and no longer used.
Example
The rapid advancement of technology leads to the obsolescence of old devices.
テクノロジーの急速な進歩は古いデバイスの陳腐化を引き起こします。
C1 noun /ˈoʊvərˌtʊr/

overture

序曲 / 提案
Meaning
An introduction to something more substantial; a proposal or preliminary action.
Example
The peace overture was welcomed by both nations.
平和提案は両国によって歓迎されました。
C1 adverb /ˈaʊtwədli/

Outwardly

外見上; 表面的に;
Meaning
on the surface; externally; in appearance
Example
Outwardly, he seemed calm, but inside he was nervous.
外見上は落ち着いて見えましたが、内心では緊張していました。
C1 noun ɔːrˈdiːl

ordeal

厳しい試練
Meaning
A physical or mental painful experience that must be endured
Example
Surviving the wilderness was a tough ordeal for them.
荒野で生き残ることは彼らにとって大変な試練でした。
C1 verb /ˌaʊtˈstrɛtʃ/

outstretch

外に伸ばす
Meaning
To extend or stretch something outward.
Example
He outstretched his hand to help her up.
彼は彼女を助けるために手を差し出した。
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 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。
C1 verb /ˌoʊvərˈθroʊ/

overthrow

幸せ
Meaning
To remove a leader or government from power, often by force.
Example
The rebels planned to overthrow the corrupt regime.
彼女は賞を受け取ったとき、幸せを隠すことができなかった。
C1 adjective /əbˈtjuːs/

Obtuse

鈍い; 理解が遅い; 愚か
Meaning
annoyingly insensitive or slow to understand; lacking in intelligence or perception
Example
He was being deliberately obtuse about the instructions.
彼は指示に関して意図的に鈍かった。
C1 adjective /ˌɑːpərˈtuːn/

opportune

適切な瞬間
Meaning
Happening at a suitable or convenient time.
Example
She arrived at an opportune moment to help.
彼女は助けるために適切な瞬間に到着しました。
C1 noun /ˈaʊtpoʊst/

outpost

前哨基地
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.
兵士たちは遠隔地の前哨基地に配置されました。
C1 adjective /ˈɒptɪkəl/

optical

光学的
Meaning
related to or used in seeing or sight
Example
The optical illusion fooled everyone at the exhibition.
その光学的錯覚は展示会で皆を騙した。
C1 adjective /əbˈnɒkʃəs/

Obnoxious

不快な
Meaning
extremely unpleasant; offensive; annoying
Example
His obnoxious behavior at the party annoyed everyone.
彼のパーティーでの非常に不快な振る舞いは、皆を困らせた。
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 /ˌəʊvərˈstɪmjʊˌleɪtɪd/

overstimulated

Meaning
Excessively excited or aroused, overwhelmed by too much stimulus.
Example
Overstimulated minds can lead to burnout and decreased productivity.
C1 noun /əˈfen.dər/

Offender

犯罪者; 法律違反者
Meaning
a person who commits an illegal act; someone who breaks the law
Example
The young offender was sentenced to community service.
その若い犯罪者はコミュニティサービスを命じられました。
C1 adjective /ˌɒbsəˈliːt/

obsolete

時代遅れ
Meaning
No longer in use or out of date.
Example
Floppy disks are now completely obsolete.
フロッピーディスクは現在完全に時代遅れです。
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。
C1 adjective /əˈblɪɡ.ə.tɔː.ri/

obligatory

義務的
Meaning
Required by a legal, moral, or other rule; compulsory.
Example
Wearing a seatbelt is obligatory in most countries.
ほとんどの国でシートベルトを着用することは義務です。
C1 adjective /aʊtˈmoʊdɪd/

outmoded

時代遅れ
Meaning
No longer in fashion or useful; outdated.
Example
That old computer is completely outmoded.
その古いコンピューターは完全に時代遅れです。
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。
C1 verb /əˈfɪʃieɪt/

officiate

執り行う
Meaning
To perform official duties, especially in a ceremony or as a referee.
Example
The priest will officiate the wedding ceremony.
司祭が結婚式を司る。
C1 noun /ɔːr/

Oar

オール
Meaning
a long pole with a flat blade used to row a boat
Example
He dipped the oar into the water and pulled the boat forward.
彼はオールを水に浸し、ボートを前に進めた。
C1 verb /ˌoʊvərˈruːl/

overrule

却下する
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.
裁判官は弁護側の異議を却下した。
C1 adjective/adverb /ˌɒfˈhænd/

offhand

軽率
Meaning
Without previous thought or preparation; casual and sometimes dismissive.
Example
She gave an offhand reply to his serious question.
彼女は彼の真剣な質問に対して、軽率な返答をした。
C1 adjective ˈɒk.sɪ.də.tɪv

oxidative

酸化に関連する
Meaning
Related to or caused by oxidation, especially cellular damage from free radicals.
Example
Excess stress can lead to oxidative damage in cells.
過度のストレスは細胞に酸化的な損傷を引き起こす可能性があります。
C1 noun /ˈɒn.slɔːt/

onslaught

猛攻
Meaning
A fierce or destructive attack.
Example
The village faced an onslaught of enemy forces.
その村は敵軍の猛攻に直面しました。
C1 noun ˈoʊʃən əˌsɪdɪfɪˈkeɪʃən

ocean acidification

海洋酸性化
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.
海洋酸性化は、大気中のCO2の吸収によって引き起こされます。
C1 noun ˌoʊ.vɚˈɡreɪ.zɪŋ

overgrazing

過剰放牧
Meaning
The practice of allowing livestock to graze to the point of damaging vegetation.
Example
Overgrazing leads to soil erosion and loss of biodiversity.
過剰放牧は土壌の浸食と生物多様性の喪失を引き起こします。
C1 verb /əˈprɛs/

oppress

抑圧する
Meaning
to keep someone down by harsh and unfair use of authority; to suppress
Example
The dictator oppressed the people for decades.
独裁者は何十年も人々を抑圧した。
C1 adjective /əbˈsɛsɪv/

obsessive

執着的
Meaning
Relating to or characterized by an obsession; thinking about something too much.
Example
He has an obsessive interest in cleanliness.
彼は清潔さに執着的な興味を持っています。
C1 verb /ˈɔːstrəˌsaɪz/

ostracize

追放する
Meaning
to exclude someone from a group or society; to banish or shun
Example
After the scandal, he was ostracized by his former colleagues.
スキャンダル後、彼は元同僚に追放された。
C1 adjective /ˌɔːrnəˈmɛntl/

ornamental

装飾的な
Meaning
Serving as decoration; decorative rather than functional.
Example
The garden was filled with ornamental plants.
庭は装飾的な植物でいっぱいだった。
C1 verb /əbˈstrʌkt/

obstruct

妨げる
Meaning
to block or hinder progress; to prevent or impede movement
Example
The fallen tree obstructed the road for several hours.
倒れた木が数時間道路をふさぎました。
C1 adjective /ɒˈstɛnsəbl/

ostensible

見せかけの
Meaning
stated or appearing to be true, but not necessarily so
Example
His ostensible reason for leaving was illness, but many doubted it.
彼の出発の見せかけの理由は病気だったが、多くの人がそれを疑っていた。