多分|たぶんtabun[1]atamadaka (head-high)

1. adverbprobably; likely; perhaps; maybe
   君きみにはたぶんみんなわかっていることでしょう。↗

   I expect you know all about it.
2. no-adjective, na-adjectivea lot of; much; many; considerable; large (amount); generous

• SynonymおそらくNeutralLike 「多分」 but slightly more formal and a touch more confident; often pairs with 「だろう」 in predictions and inferences.
• SynonymおそらくはWrittenAn emphatic written form of 「恐らく」, found mainly in prose; in everyday speech 「多分」 is the natural choice.
• Antonym必ずかならずNeutralContrasts with the conjecture of 「多分」: it asserts that something happens without fail, with no uncertainty.
• Antonym確実かくじつNeutralThe opposite of 「多分」: it describes something certain and dependable, as in 「確実な情報」.
• Antonym間違いなくまちがいなくNeutralAlso opposed to 「多分」: it asserts that something is definitely so, with no room for doubt.

For everyday guesses, 「多分」 is the default. Use 「恐らく」 in writing or for a more serious tone (its emphatic written form 「恐らくは」 turns up in prose). For certainty rather than conjecture, switch to 「必ず」 or 「間違いなく」, and 「確実」 for something sure and reliable.

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

1. 断言だんげんできないがそうなる見込みこみが大おおきいと話者わしゃが推量すいりょうする様子ようす。おそらく。
2. 量りょうが多おおいこと。比率ひりつが大おおきいこと。
3. かなりの程度ていどであること。
4. 大部分だいぶぶん。大多数だいたすうの人ひとや物もの。