いつでも・何時でもitsudemo

1. adverbalways; all the time; at all times
   私はいつでも喜よろこんでお手伝てつだいします。↗

   I am always ready to help you.
2. adverb(at) any time; whenever (you like)
   あなたはいつでも歓迎かんげいされています。↗

   You will be welcome at any time.

• Synonym常々つねづねWrittenA written/formal word for what one usually does or feels, as in 「常々思っている」; it often goes with verbs of thinking, unlike the anytime sense of 「いつでも」.
• Synonym絶えずたえずWrittenMeans constantly, without interruption, as in 「絶えず変化する」; it stresses unbroken continuity rather than availability at any time.
• Synonym常につねにNeutralNeutral but leaning written; means always, at all times, as in 「常に注意する」. 「いつでも」 instead says that any time will do.
• SynonymいつもNeutralThe everyday word for always or habitually, as in 「いつも遅刻する」; it stresses habit, while 「いつでも」 stresses that any time is fine.
• Synonym明け暮れあけくれWrittenWritten/formal prose: as a noun it means morning and evening, daily life; 「明け暮れする」 means spending whole days on one thing. It never means any time is fine.
• Synonym始終しじゅうNeutralMeans from beginning to end, or constantly, as in 「始終笑っている」; it stresses the whole span of time rather than availability.
• Synonym四六時中しろくじちゅうCasualColloquial for around the clock, every moment of the day, as in 「四六時中スマホを見る」.
• SynonymしょっちゅうCasualColloquial for constantly or very often, as in 「しょっちゅう電話する」; the stress is on frequency, not on any time being fine.
• Synonym年中ねんじゅうNeutralMeans all year round, as in 「年中無休」, and by extension always; 「いつでも」 is about any time being fine, not about the whole year.
• SynonymずっとNeutralMeans the whole time, continuously, as in 「ずっと待っている」; it stresses unbroken duration rather than availability.
• Synonym絶え間なくたえまなくNeutralMeans incessantly, with no gaps, as in 「絶え間なく雨が降る」; the stress is on there being no pause at all.
• Synonym年がら年中ねんがらねんじゅうCasualColloquial for all year round, as in 「年がら年中忙しい」; it often carries an exaggerated tone of complaint, which 「いつでも」 does not.
• Synonym年百年中ねんびゃくねんじゅうCasualColloquial and old-fashioned, meaning all year round, always; rarely used today.
• SynonymのべつまくなしCasualColloquial for nonstop, without a break, as in 「のべつ幕なしに喋る」; it is mostly about endless talking, not about timing.
• SynonymのべつCasualColloquial for ceaselessly, as in 「のべつ文句を言う」; it carries a tone of displeasure.
• Synonym明けても暮れてもあけてもくれてもNeutralDay in, day out, as in 「明けても暮れても仕事」; it describes the same thing continuing from morning to night, every day.
• Related決まってきまってNeutralMeans invariably, every single time, as in 「雨の日は決まって頭痛がする」; the point is regularity, not that any time will do.
• RelatedとめどなくWrittenWritten/formal prose for endlessly, unstoppably, as in 「涙がとめどなく流れる」; it is used mostly of tears and words.
• Related朝夕あさゆうWrittenWritten/formal prose for morning and evening, as in 「朝夕の冷え込み」; it can also mean constantly.
• Related日夕にっせきWrittenA rare written/formal word for day and night; in everyday speech, morning and evening is 「朝晩」.
• Related常住坐臥じょうじゅうざがWrittenA four-character idiom, strongly written/formal: at all times, in the midst of daily life, sitting or lying down.
• Related間断なくかんだんなくWrittenWritten/formal prose for continuously, without interruption, as in 「間断なく続く」.
• Antonym決してけっしてNeutralWith a negative it means never, absolutely not, as in 「決して遅れない」; it is the opposite of 「いつでも」 in the always, any time sense.
• Antonym一度もいちどもNeutralWith a negative it means not even once; it stands opposite to the every time, always sense of 「いつでも」.

Use 「いつでも」 when any time will do, as in 「いつでも来て」. For the habitual always use 「いつも」, in written prose 「常に」, for frequency the colloquial 「しょっちゅう」, for invariable regularity 「決まって」. 「年がら年中」「年中」 mean all year round and 「四六時中」 around the clock; 「ずっと」「始終」「絶えず」「絶え間なく」「間断なく」 stress unbroken continuity. Written/formal terms include 「常々」「明け暮れ」「朝夕」「日夕」「常住坐臥」「止めどなく」; colloquial ones include 「年がら年中」「四六時中」「のべつ」「のべつ幕なし」「年百年中」. The antonyms 「決して」「一度も」 take a negative to mean never.

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

1. どんな時ときでも。常つねに。