Grammar Point
expressions (phrases, clauses, etc.)
exp 
か(どうか)

whether or not (in phrases like "I don't know whether or not I can come")

Verb / い-Adjective + か (どうか)

This structure is used to embed a yes-no question into a larger sentence. It translates to 'whether or not' or 'if' in English. While どうか is often used to emphasize the 'or not' part, it is optional and frequently omitted in casual speech.

Verb (Informal)

Verbs in their informal form (present or past) are followed by か or かどうか to create an embedded question.

I don't know whether he will come or not.

Please tell me if you ate it.

い-Adjective

い-adjectives in their informal form are followed directly by か or かどうか.

I don't know if it is delicious or not.

Note

The particle どうか is more formal and is typically used when the speaker is unsure about a specific outcome.

Noun / な-Adjective + か (どうか)

For nouns and な-adjectives, the copula だ is dropped in the present tense before adding か or かどうか. In the past tense, the informal past form だった is used.

Noun or な-Adjective stem

The stem of a な-adjective or a noun is used directly for the present tense, or the past form だった is used for the past tense.

I am checking whether it is convenient or not.

I don't know if he was a student.

Note

Though in the informal form, the present tense of な-adjectives and nouns does not take だ before か. For example, use 好きか instead of 好きだか.です is never used in an embedded question; the informal form is always used.

Words: 
かどうか
Radicals of radicals