GRAMMAR DETAIL

かどうか

whether or not ...

Turns two unresolved possibilities into an embedded question within a sentence.

Examples

この薬を食後に飲むかどうか、説明書で確認した。

I checked the instructions to see whether or not this medicine should be taken after meals.

申込書が届いたかどうか、電話で確認した。

I called to confirm whether or not the application form had arrived.

明日参加できるかどうか、今夜連絡します。

I will let you know tonight whether or not I can participate tomorrow.

Structure: かどうか follows plain-form content and packages its positive and negative possibilities as an embedded question.
Basic usage: 申込書が届いたかどうか、電話で確認した。 means checking whether the application form had arrived.

Unlike a question with an interrogative word
- 届いたかどうか asks whether it arrived or not. To ask when it arrived, use an interrogative with か, as in いつ届いたか; the answer is a time, not one of two alternatives.
Omitting da after nouns and na-adjectives
- Omit だ after present affirmative nouns and na-adjectives, as in 学生かどうか or 必要かどうか. Keep past だった, as in 学生だったかどうか.