余談|よだんyodan[0]heiban (flat)

1. noundigression
   余談よだんだが、この念ねん発火はっか能力のうりょくのことをパイロキネシスというらしい。↗

   By the by, this ability to will fire into existence is apparently called pyrokinesis.

• Related逸脱いつだつWrittenWritten/formal word for deviation from a norm or standard, stressing overstepping the bounds; not specifically about topics of conversation.
• Related脱線だっせんNeutralLiterally a train derailment; colloquially, talk drifting off topic, stressing that the speaker strays without noticing.
• Related脇道わきみちNeutralLiterally a side road; figuratively a topic straying off course, as in 「話が脇道にそれる」. Unlike 余談, it does not imply a deliberately inserted aside.
• Antonym本題ほんだいNeutralThe main subject at hand, the opposite of an aside like 余談, as in 「本題に入る」.
• Antonym本論ほんろんWrittenThe main argument or body of a written work; the written-prose counterpart of 余談.

Use 「余談」 for an aside you deliberately insert, often as 「余談ですが」. For talk that drifts off topic say 「脱線」, and for a topic branching off say 「脇道にそれる」; the opposite pole is 「本題」.

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

1. 余分よぶんな話はなし。余計よけいな話はなし。つまらない話はなし。トリビア。（ただし、余談よだんの方ほうが本論ほんろんより面白おもしろいことは多おおい。）
2. 「余談よだんだが/ですが/ではあるが」等とうで始はじまる本論ほんろん・本筋ほんすじでない話はなし。