How to say "certainty" in Japanese
Choosing the right word
- 定じょうnounGlossed 'certainty' but also 'reality' and 'actuality'; in practice it is not used as an independent word, so it is seldom the word you want for 'certainty'.
- 確実性かくじつせいnounCertainty as an abstract quality — the state of being sure, certain, or reliable. The word you want when discussing how certain something is, such as whether a plan or report can be relied on.
- 確実度かくじつどnounCertainty as a matter of degree — how certain something is, rather than whether it is certain. Use it when you want to speak of the level or extent of certainty.
For certainty as an abstract quality use 確実性; for certainty expressed as a degree or level use 確実度; 定, though also glossed 'reality' and 'actuality', is not a word you can use on its own.
Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only
Japanese equivalents
