開始|かいしkaishi[0]heiban (flat)

1. noun, suru verb, transitive verb, intransitive verbstart; commencement; beginning; initiation
   何時いつに搭乗とうじょう開始かいしですか。↗

   What time does boarding begin?

• Synonym始めるはじめるNeutralEveryday transitive verb, the most common choice in speech, as in 「仕事を始める」. 開始 is a Sino-Japanese noun favoured in formal announcements like 「試合開始」.
• SynonymスタートNeutralLoanword common in casual speech; also covers departing and the starting line, as in 「スタートを切る」. 開始 sounds more formal.
• Synonym着手ちゃくしゅWrittenWritten word for setting to work on a task, as in 「工事に着手する」; it stresses getting hands on the job. 開始 is not limited to work.
• Synonym始動しどうWrittenWritten word for a machine starting up or a plan going into action, as in 「プロジェクト始動」; stresses beginning to operate, often in news headlines.
• Synonym始まるはじまるNeutralEveryday intransitive verb for something beginning, as in 「授業が始まる」; the most common way to say it in speech. 開始 is mostly a noun or used as 「開始する」.
• Synonym始まりはじまりNeutralNoun for the beginning or origin of something, as in 「物語の始まり」, common in speech. 開始 points to the moment an activity starts.
• SynonymキックオフNeutralOriginally the kickoff in football; by extension the launch of a project or event, as in 「キックオフミーティング」; mostly business use.
• Synonym仕掛けるしかけるNeutralCan neutrally mean starting something and being partway through, but also picking a fight or setting a trap, as in 「罠を仕掛ける」; 開始 is simply neutral.
• Synonym取り掛かるとりかかるNeutralFor getting down to a task, as in 「作業に取り掛かる」; common in speech and close to 着手 but more everyday.
• SynonymはじめNeutralNoun for the beginning or first part of a period, as in 「年の始め」; points to the front end in time, while 開始 is the act of starting.
• Synonym発足ほっそくWrittenWritten word for an organization or movement officially starting up, as in 「新内閣が発足する」; stresses an organized launch. 開始 has no such limit.
• Related始業しぎょうWrittenWritten word limited to the start of the workday or school term, as in 「始業式」「始業時間」.
• Related創始そうしWrittenWritten word for founding or creating something for the first time, as in 「創始者」; stresses pioneering. 開始 simply means starting something.
• Related踏み出すふみだすNeutralLiterally to step forward; figuratively to take the first step toward something new, as in 「第一歩を踏み出す」, with a nuance of resolve.
• Related起動きどうNeutralFor starting machines or computers, as in 「パソコンを起動する」; its objects are limited to devices and software.
• Related当初とうしょNeutralRefers to the initial stage or what was planned at first, as in 「当初の予定」; often adverbial, but never the act of starting itself.
• Relatedし始めるしはじめるNeutralAttaches to an action to mean beginning to do it, as in 「勉強し始める」; highlights the starting point of the action and is common in speech.
• RelatedしだすCasualColloquial: begins doing something one had not been doing, often with a sudden feel; also means to cater, making and delivering food.
• RelatedやりだすCasualColloquial for getting started on something, often with a sudden or unexpected tone; far more casual than 開始.
• Related幕開きまくあきWrittenLiterally the curtain rising; a literary metaphor for the dawn of an era or event, as in 「新時代の幕開き」.
• Related出だしでだしCasualColloquial noun for the opening stretch of something or the start of a song, as in 「出だしは順調」; focuses on how the beginning goes.
• RelatedおっぱじめるCasualCoarse colloquialism for starting something abruptly or in earnest, as in 「喧嘩をおっ始める」; avoid in formal settings.
• Related滑り出しすべりだしNeutralNoun for how something starts off, as in 「滑り出しは好調」; used to judge whether the start went well, not the act of starting itself.
• Relatedやり始めるやりはじめるNeutralColloquial for starting to do something, close to 「し始める」 and more casual than 開始.
• Antonym終了しゅうりょうNeutralThe formal counterpart for ending an activity, as in 「試合終了」; pairs with 開始 as the standard formal way to mark the end.
• Antonym終わりおわりNeutralEveryday word for the end, used in both speech and writing; the natural opposite of 開始 and 「始まり」.
• Antonym閉幕へいまくWrittenWritten word for a performance or tournament closing, as in 「大会が閉幕する」; stands opposite 開始 for the start of an event.

For everyday speech pick 「始める」/「始まる」; 「開始」 is the formal Sino-Japanese word of announcements like 「試合開始」. 「スタート」 is the casual loanword. To say you begin doing something, use 「し始める」/「やり始める」. For setting to work use 「着手」 or 「取り掛かる」; for organizations 「発足」; for machines 「起動」/「始動」; for business launches 「キックオフ」. As nouns for beginnings, 「始まり」「始め」「当初」; sudden colloquial starts are 「し出す」「やり出す」「おっ始める」. Antonyms: formal 「終了」, everyday 「終わり」, event-closing 「閉幕」.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

1. 何なんかが始はじまること。
2. 何なんかを始はじめること。