かどうか

1. Construction
かどうか attaches directly to the plain form of verbs and adjectives. For nouns and な-adjectives in the present tense, you must drop the だ. However, in the past tense, the た form (including だった for nouns/な-adjectives) is retained. This applies to negative forms as well.

• Verbs: Plain Form + かどうか (e.g., 行く（いく）かどうか (whether to go) / 行った（いった）かどうか (whether went) / 行かない（いかない）かどうか (whether not to go))
• い-Adjectives: Plain Form + かどうか (e.g., 美味しい（おいしい）かどうか (whether it is delicious) / 美味しかった（おいしかった）かどうか (whether it was delicious) / 美味しくない（おいしくない）かどうか (whether it is not delicious))
• な-Adjectives: Stem (No だ) + かどうか (e.g., 好き（すき）かどうか (whether you like it) / 好きだった（すきだった）かどうか (whether you liked it) / 好きじゃない（すきじゃない）かどうか (whether you don't like it))
• Nouns: Noun (No だ) + かどうか (e.g., 学生（がくせい）かどうか (whether they are a student) / 学生だった（がくせいだった）かどうか (whether they were a student) / 学生じゃない（がくせいじゃない）かどうか (whether they are not a student))

2. Usage
The entire clause ending in かどうか acts like a noun. This means it can be followed by particles like が (subject), を (object), or は (topic), depending on the main verb of the sentence (e.g., 分かる（わかる） (to understand), 知る（しる） (to know), 確かめる（たしかめる） (to confirm), 聞く（きく） (to ask), 迷う（まよう） (to hesitate), 調べる（しらべる） (to investigate)). In casual speech, these following particles are frequently omitted. Additionally, the subject inside the embedded かどうか clause almost always takes が instead of は (e.g., 田中（たなか）さんが学生（がくせい）かどうか分からない (I don't know whether Tanaka-san is a student or not), not 田中さんは...).

3. Nuance and Alternatives
While English often just uses 'if,' Japanese uses かどうか to clearly signal that both options (yes and no) are being weighed. The phrase どうか literally means 'how [it is],' so the pattern is essentially asking 'is it [X] or how [is it]?' It is often used as a shorthand for repeating the verb in its negative form, such as 行くか行かないか（いくかいかないか） (whether to go or not go). In casual speech, the どうか is often dropped for yes/no questions (e.g., 行く（いく）か分からない（わからない） (I don't know if I will go)), making the sentence lighter. In more formal or written contexts, you may see the alternative か否か（かいなか） (whether or not) used instead of かどうか. You will also frequently hear the variation のかどうか / なのかどうか (e.g., 行く（いく）のかどうか (whether to go or not), 学生（がくせい）なのかどうか (whether they are a student or not)), which adds an explanatory or inquisitive tone, similar to the んです pattern.

4. Restriction on Question Words
Unlike the embedded question pattern using just か, you cannot use question words (interrogatives) like いつ, どこ, or 何（なに） with かどうか. For questions involving 'who,' 'what,' 'where,' etc., use the 疑問詞 + か pattern instead. Note that for simple yes/no questions, you can use either かどうか or just か.