oakum
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C2 noun /ˈoʊ.kəm/

oakum

古いロープの繊維
Meaning
loose fibers obtained by untwisting old ropes, used for caulking ships
Example
The shipbuilders used oakum to seal the gaps in the wooden planks.
船大工たちは木の板の隙間を塞ぐためにオーカムを使いました。
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。
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。
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。
B2 verb /ˌoʊvərˈwɛlm/

overwhelm

Meaning
to overpower someone emotionally or physically; to be too much to handle
Example
She was overwhelmed with gratitude after receiving the help.
C2 noun /ˈoʊvərlɔːrd/

overlord

領主
Meaning
A ruler, master, or person of great power and authority over others.
Example
The peasants were forced to pay taxes to their overlord.
農民たちは自分たちの領主に税金を払うよう強制されました。
A1 pronoun /aʊər/

our

私たちの
Meaning
belonging to or associated with the speaker and one or more other people
Example
This is our house.
これは私たちの家です。
C2 adjective /ˈoʊ.pən ˈhæn.dɪd/

Open-handed

寛大な; 自由な
Meaning
Generous; liberal; giving freely;
Example
He is very open-handed with his money and always helps those in need.
彼は自分の金に非常に寛大で、いつも困っている人々を助けています。
B2 noun /ˈaʊt.saɪ.dər/

Out-sider

アウトサイダー
Meaning
a person who does not belong to a particular group; someone not accepted by a group
Example
As an outsider, he found it difficult to understand their traditions.
アウトサイダーとして、彼は彼らの伝統を理解するのが難しいと感じました。
C2 verb /ˈɑːbdʒərˌɡeɪt/

objurgate

厳しく叱る
Meaning
to scold or rebuke severely
Example
The teacher objurgated the student for being dishonest.
先生は不正直な生徒を厳しく叱った。
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。
B2 noun /ˈaʊtˌsɛt/

outset

開始
Meaning
the beginning or start of something
Example
From the outset, the project seemed ambitious but achievable.
最初から、プロジェクトは野心的だが達成可能に見えました。
A1 pronoun, noun, adjective /wʌn/

one

一
Meaning
the number equivalent to the sum of zero and one; a single person or thing
Example
Only one student answered the question.
ただ一人の学生が質問に答えました。
A1 adjective /əʊˈkeɪ/

okay

大丈夫
Meaning
used to express agreement or acceptance
Example
It's okay to leave early today.
今日は早く帰るのは大丈夫です。
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 /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 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。
A2 adjective /ˈɔː.dɪ.nər.i/

Ordinary

普通の; 一般的な; 特別ではない
Meaning
normal; usual; not special
Example
It was just an ordinary day at the office.
それはオフィスでのただの普通の日でした。
B1 verb /oʊ/

owe

借りがある
Meaning
to be under obligation to pay or repay; to be indebted
Example
I owe my success to my parents' support.
私は両親の支援のおかげで成功しました。
B1 adjective /əˈbiː.di.ənt/

Obedient

従順な
Meaning
willing to comply with orders or instructions; submissive
Example
The obedient student always follows the teacher's instructions.
従順な生徒はいつも先生の指示に従う。
B2 noun /əˈfɛns/

offense

犯罪
Meaning
an illegal act; a crime
Example
The offense was committed in broad daylight.
その罪は昼間に犯されました。
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。
C2 noun /ˈɒbsɪkwi/

obsequy

葬儀
Meaning
A funeral rite, usually used in plural form obsequies.
Example
The village gathered for the obsequy of their beloved teacher.
村人たちは、愛する教師の葬儀のために集まりました。
B2 verb /əˈfend/

offend

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。
B1 verb অকার্স

occurs

起こる
Meaning
Happens or takes place, especially as a result of something.
Example
Snowfall occurs in regions with freezing temperatures.
雪は氷点下の温度を持つ地域で起こります。
C1 noun /ɒpˈtɒmɪtrɪst/

optometrist

オプトメトリスト
Meaning
A healthcare professional who examines eyes and prescribes corrective lenses.
Example
The optometrist prescribed new glasses for her.
オプトメトリストは彼女に新しい眼鏡を処方しました。
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。
B1 noun /əˈkeɪ.ʒən/

Occasion

機会; 特別な出来事
Meaning
a particular time or instance of an event; a special celebration
Example
Their wedding was a joyous occasion.
彼らの結婚式は喜ばしい機会でした。
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。
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。
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。
C2 adjective /ˈɑːbdjʊrət/

obdurate

頑固
Meaning
Stubbornly refusing to change one's opinion or course of action.
Example
He remained obdurate despite everyone's pleas.
彼は皆の懇願にもかかわらず、頑固なままでした。
B1 noun ˈɒk.sɪ.dʒən

oxygen

酸素。無色無臭の気体で、生命に不可欠な成分です。
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.
酸素は生命にとって不可欠です。
A1 pronoun /ˈʌðərz/

others

他の人々
Meaning
people or things distinct from the ones already mentioned or known
Example
I like to spend time with others.
私は他の人々と時間を過ごすのが好きです。
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。
C2 verb /ˈɔːreɪt/

orate

演説する
Meaning
To speak in a formal, often pompous manner
Example
He began to orate at the ceremony.
彼は式で演説を始めました。
C2 noun /ˈɔɪl.mən/

Oilman

石油業者
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.
オイルマンは砂漠で新しい油田を発見した。
B1 adverb /ˈʌðərwaɪz/

Otherwise

さもないと; 他の方法で
Meaning
in a different way; if not; or else; apart from that
Example
Study hard, otherwise you will fail the exam.
一生懸命勉強しなさい、さもないと試験に落ちます。
C2 adjective /ˈɒfɪʃ/

offish

無愛想
Meaning
Unfriendly, distant, or reserved in manner.
Example
He seemed offish at the party and avoided most conversations.
彼はパーティーで無愛想に見え、大半の会話を避けていました。
C2 adjective /ˈɒkjʊlər/

ocular

眼科の
Meaning
Relating to the eye or vision.
Example
The patient was referred to a specialist for ocular treatment.
患者は眼科専門医に紹介されました。
B1 noun ˌɔː.ɡən.aɪˈzeɪ.ʃən

organization

組織
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.
その組織は2024年に公式に開設されました。
C1 noun /ˈoʊ.mən/

Omen

未来の良いまたは悪い運命の兆し
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.
多くの人々は、黒猫が道を横切ることを悪いオーメンだと考えています。
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。
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。
C2 verb /ˈɑːblɪˌɡeɪt/

obligate

強制する
Meaning
to bind legally or morally; to compel someone to do something
Example
The contract obligates the company to provide timely service.
契約は会社にタイムリーなサービスを提供することを義務付けます。
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。
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 /ˌɒbstəˈtrɪʃən/

obstetrician

産科医
Meaning
A doctor specializing in pregnancy, childbirth, and women's reproductive health.
Example
The obstetrician monitored the mother’s health throughout the pregnancy.
産科医は妊娠中の母親の健康を監視しました。
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。
A2 noun əˈlɪm.pɪk ɡeɪmz

Olympic Games

オリンピック競技大会
Meaning
The world's largest international sports competition held every four years, bringing together athletes from different countries to compete in various sports.
Example
The Olympic Games bring together the world's top athletes.
オリンピック競技大会は世界のトップアスリートを集めます。
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。
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。
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。
C2 noun /ɔːˈreɪʃən/

oration

演説
Meaning
A formal speech, especially one given on a ceremonial occasion
Example
The president delivered an inspiring oration.
大統領は感動的な演説を行いました。
C2 noun /oʊˈbleɪʃən/

oblation

奉納
Meaning
a religious offering, especially of bread or wine to God
Example
The priest placed the oblation on the altar during the ceremony.
司祭は儀式の間に祭壇に奉納を置きました。
B2 adjective /əˈpəʊzd/

opposed

反対の
Meaning
being against or in disagreement with something
Example
She is strongly opposed to animal testing.
彼女は動物実験に強く反対しています。
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。
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。
A2 adverb; noun /ˌaʊtˈdɔːrz/

outdoors

屋外で
Meaning
outside a building; the natural environment outside
Example
We spent the whole afternoon outdoors enjoying the fresh air.
私たちは午後ずっと屋外で新鮮な空気を楽しみました。
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 /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 /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。
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 /ˈoʊɡər/

ogre

Meaning
A mythical monster, often depicted as large, hideous, and cruel; metaphorically, a cruel or terrifying person.
Example
The villagers feared the ogre who lived in the dark forest.
B2 noun /ˌoʊ.vɚˈkraʊ.dɪŋ/

overcrowding

過密
Meaning
Excessive crowd or packed condition, having more people or vehicles in a place than the approved capacity.
Example
The subway system suffers from severe overcrowding during peak hours.
地下鉄システムはピーク時にひどい過密状態に苦しんでいます。
C1 verb /ˈoʊvərˌhɔːl/

overhaul

完全な改修
Meaning
to examine thoroughly and repair or improve something that is worn or ineffective
Example
The company decided to overhaul its outdated computer system.
会社は古くなったコンピュータシステムのオーバーホールを決定した。
C2 noun /ˈɔːfəl/

offal

内臓
Meaning
the internal organs and entrails of an animal used as food; waste parts
Example
The butcher prepared sausages using pork offal.
肉屋は豚の臓物を使ってソーセージを作った。
A1 interjection /oʊ/

oh

オー
Meaning
used to express surprise, realization, or understanding
Example
Oh, I didn't know you were here!
オー、あなたがここにいるとは思わなかった！
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。
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。
B2 adverb /ˈɒdli/

oddly

奇妙に
Meaning
in a strange or unusual way; unexpectedly
Example
Oddly, he didn’t seem upset by the bad news.
奇妙に、彼は悪い知らせにも動揺していなかった。
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。
A1 adjective /ˈɔːr.ɪndʒ/

Orange

オレンジ色
Meaning
having a color between red and yellow like that of a ripe orange fruit
Example
The orange sunset painted the sky magnificently.
オレンジ色の夕日は空を素晴らしく彩った。
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。
B2 verb /ˌoʊvərˈiːt/

overeat

幸福
Meaning
To eat more food than the body needs.
Example
She tends to overeat when she is stressed.
彼女は賞を受け取ったとき、喜びを隠すことができませんでした。
B2 noun /ˌɑb.lɪˈɡeɪ.ʃən/

Obligation

義務
Meaning
a duty or commitment; something that must be done legally or morally
Example
Parents have an obligation to care for their children.
親は子供の世話をする義務がある。
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。
B2 noun /əˈfens/

Offence

違反; 犯罪
Meaning
a breach of law or rule; an annoyance or resentment
Example
Stealing is a serious offence punishable by law.
窃盗は法律で罰せられる重大な違反です。
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。
C2 noun /ˌɒstɛnˈteɪʃən/

ostentation

見せびらかし
Meaning
excessive display of wealth or knowledge intended to attract admiration or envy
Example
The billionaire’s party was full of ostentation and luxury.
億万長者のパーティーは、見せびらかしと贅沢で満ちていた。
C2 noun /ˈɔːrzmən/

Oarsman

オールマン
Meaning
a person who rows a boat, especially as a member of a racing crew
Example
The experienced oarsman rowed the boat across the river.
経験豊富なオールマンは川を渡るためにボートを漕いだ。
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。
B2 verb /ˌoʊvərˈsiː/

oversee

監督する
Meaning
to supervise or watch over something; to manage and direct
Example
The manager will oversee the entire construction project.
マネージャーは全体の建設プロジェクトを監督します。
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 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 /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。
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。
B2 verb /ˌoʊvərˈloʊd/

overload

過負荷
Meaning
to load with too much weight or cargo; to give too much work or information
Example
Don't overload the washing machine or it might break down.
洗濯機をオーバーロードしないでください、壊れるかもしれません。
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。
C2 adjective /ˈoʊ.kən/

oaken

オーク材で作られた
Meaning
made of or resembling oak wood
Example
The villagers gathered around the oaken table in the hall.
村人たちはホールの中のオーク材のテーブルの周りに集まりました。
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。
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。
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。
A2 adjective /ɒd/

Odd

奇妙な; 異常な; 正常または予想されるものとは異なる
Meaning
strange; unusual; different from what is normal or expected
Example
That's an odd way to solve the problem.
それは問題を解決する奇妙な方法です。
B2 adjective /ˈaʊtˌɡoʊɪŋ/

outgoing

社交的
Meaning
Friendly and sociable; inclined to mix with others.
Example
He is an outgoing person who loves meeting new people.
彼は新しい人々と会うのが好きな社交的な人です。
B2 noun/verb /ˌoʊvərˈlæp/

overlap

Meaning
To extend over and cover partly; an area where things coincide.
Example
The two meetings overlap by an hour.
B1 adjective /ˌoʊvərˈsiːz/

overseas

海外
Meaning
in or to a foreign country across the sea
Example
He went overseas for higher education.
彼は高等教育のために海外に行った。
B2 noun /ɔːˈræŋ.ʊˌtæŋ/

Orang-Outang

オランウータン
Meaning
a large arboreal ape with long reddish hair, long arms, and hooked hands and feet, native to Borneo and Sumatra
Example
The orangutan swings gracefully through the forest canopy.
オランウータンは森の樹冠を優雅に渡ります。
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。
C2 noun /ˈoʊpiət/

opiate

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.
B2 noun /ɑːks/

Ox

雄牛
Meaning
a large strong animal used for pulling heavy loads or plowing fields
Example
The farmer used an ox to plow the field.
農夫は畑を耕すために雄牛を使いました。
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。
A1 preposition, adverb /ˈoʊvər/

over

上に
Meaning
across, on top of, or beyond
Example
The book is lying over the table.
本はテーブルの上にあります。
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。
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。
C2 adjective /ɒˈstɛnsɪv/

ostensive

明示的
Meaning
clearly demonstrative or pointing out; explicitly shown
Example
The teacher gave an ostensive example to clarify the concept.
先生はその概念を明確にするために、明示的な例を示しました。
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。
A1 preposition /ɒn/

on

上
Meaning
physically in contact with and supported by a surface
Example
The book is on the table.
本はテーブルの上にあります。
B2 adjective, verb /əbˈskjʊr/

obscure

不明確
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.
詩の意味はほとんどの読者には不明確でした。
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。
C2 noun /ˈɒfərtɔːri/

offertory

奉納
Meaning
The part of a religious service when offerings are collected; the offering itself.
Example
The offertory was taken during the Sunday service.
日曜日の礼拝中に奉納が取られました。
B1 noun /ˈɒbstəkəlz/

obstacles

障害物
Meaning
Things that block one's way or prevent or hinder progress.
Example
Obstacles in life can often lead to valuable lessons.
人生の障害物はしばしば貴重な教訓に繋がる。
B2 adjective ɔːrˈɡæn.ɪk

organic

有機
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.
有機農業は土壌の健康を改善し、汚染を減少させます。
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。
C2 verb /əbˈtruːd/

obtrude

押し付ける
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.
彼は彼らのプライベートな会話に押し付けたくなかった。
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。
A2 noun /ˈoʊ.ʃən/

ocean

海洋
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.
海洋は地球の表面の70％以上を覆っています。
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。
A1 verb, adjective /oʊn/

own

所有する
Meaning
to possess something; belonging to oneself
Example
She owns a beautiful house in the city.
彼女は市内に美しい家を持っています。
A1 preposition /ʌv/

of

の
Meaning
expressing the relationship between a part and a whole
Example
The book is on the table, in front of the window.
本はテーブルの上にあり、窓の前にあります。
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.