「時間」 (jikan) has two main meanings: "time" in general, and "hours" when counting duration. As "time," it can be used to ask or talk about what time it is. As "hours," it helps express duration. For example, 「日本語を３時間勉強しました。」(Nihongo o san-jikan benkyō shimashita.) means "I studied Japanese for 3 hours."

時間は「時」や「何時間」と使います。日本語を3時間勉強しました。