〜かどうか ka dou ka
〜かどうか（ka dou ka）means “whether (or not)”. Expresses an embedded yes/no question — 'whether or not' something is the case. Formation: V/Aい（普通形）＋かどうか ／ Aな・N（語幹）＋かどうか（だ をとる）
whether (or not)
N4Formation
V/Aい（普通形）＋かどうか ／ Aな・N（語幹）＋かどうか（だ をとる）
Explanation
Expresses an embedded yes/no question — 'whether or not' something is the case. The clause before かどうか is a plain-form statement; with na-adjectives and nouns, the plain だ is dropped before か. Often followed by verbs of thinking, knowing, or checking (わからない, 知らない, 確認する).
Examples
Note
For na-adjectives/nouns, no だ: 安全かどうか, 学生かどうか. When the embedded question already has a question word (誰, いつ…), use plain か instead of かどうか.
FAQ
〜かどうか — what does it mean and how is it used?
whether (or not). Expresses an embedded yes/no question — 'whether or not' something is the case. The clause before かどうか is a plain-form statement; with na-adjectives and nouns, the plain だ is dropped before か. Often followed by verbs of thinking, knowing, or checking (わからない, 知らない, 確認する).
〜かどうか — how do you form it?
V/Aい（普通形）＋かどうか ／ Aな・N（語幹）＋かどうか（だ をとる）
〜かどうか — any usage notes?
For na-adjectives/nouns, no だ: 安全かどうか, 学生かどうか. When the embedded question already has a question word (誰, いつ…), use plain か instead of かどうか.