か否か【かいなか】

The expression か否か (かいなか) means "whether or not" and is used to present a binary question – whether something is the case or not. It is the formal, literary equivalent of the more common かどうか and is primarily found in written language, such as academic papers, legal documents, news articles, and formal speeches.

Structure

か否か attaches to the plain form of verbs, adjectives, and nouns:

• Verb (plain form)

  • か否か
    さんか参加するかいな否かはほんにん本人がきめる決めることだ。

    Whether or not to participate is something the person themselves decides.

• い-adjective

  • か否か
    このほうほう方法がただしい正しいかいな否かをけんしょう検証するひつよう必要がある。

    We need to verify whether or not this method is correct.

• な-adjective / Noun

  • であるか否か
    かれ彼がゆうざい有罪であるかいな否かはさいばん裁判できまる決まる。

    Whether or not he is guilty will be decided at trial.

Usage notes

か否か is functionally identical to かどうか in meaning, but carries a significantly more formal and stiff tone. In everyday conversation, かどうか is almost always preferred. Using か否か in casual speech would sound unnatural or overly literary.

The clause ending in か否か typically functions as a noun clause – it can serve as the subject or object of the main sentence, often followed by particles like は, を, or が.

Comparison with かどうか

Both か否か and かどうか mean "whether or not," but:

• か否か – formal/written; used in official, academic, or literary contexts
• かどうか – neutral; appropriate for both spoken and written language

Compare: ごうかく合格したかどうかはらいしゅう来週はっぴょう発表される。 (same meaning, but more neutral in tone)