未定義 undefined

Language
html
Surface
keywords
Locale
nan
Concept
undefined
Brain ID
html/keywords/undefined
Upstream reference
MDN · deep
Brain version
1.1.0-alpha.13 · generated Mon, 20 Jul 2026 15:26:24 GMT · hash 4914b8003cdd29d0…

Provenance

Full per-leaf change history across brain builds is not yet recorded; shown is the current build's layer stack.

Discuss this term on the NADA forum →

Across locales

What each covering migration carries for this concept, per locale — the whole-brain view, not filtered by your language. Forms are the migration's leaf values (pre-transform, pre-human-verdict); a locale without a form falls back to canonical English. Chips open that locale's live docs page for this term.

null-absence · concept undefined — per-locale forms

Expand to load the per-locale matrix.

demo-alpha · concept undefined — per-locale forms

Expand to load the per-locale matrix.

sealion-refinement · concept undefined — per-locale forms

Expand to load the per-locale matrix.

AI council review

Reviewed by 1 model · @cf/aisingapore/gemma-sea-lion-v4-27b-it · 2026-07-17

Cluster null-absence · locale nan · member undefined

confirm
verdict
未定
existing translation
未定
improved translation
Explanation

「未定」 effectively captures the meaning of 'not yet defined' or 'not yet assigned', which is the key distinction for 'undefined'.