What it means
もちろん means “of course” or “certainly.” It shows that the speaker considers something obvious, expected, or strongly accepted. It commonly appears at the beginning of a sentence, often followed by a pause, and can express agreement with a request, question, or statement. The result may sound confident, but the exact nuance depends on context: it can be warm and reassuring, or it can suggest that the answer should have been obvious.
Usage note
もちろん is an adverb and does not itself change between familiar and polite speech. The politeness of the complete sentence comes from the predicate that follows it. Avoid assuming that もちろん always sounds friendly; in some contexts, especially when answering an obvious question, it can sound impatient or slightly sarcastic.
How to use it
もちろん、私はその提案に賛成します。
Of course, I agree with that proposal.
もちろん、私はその提案に賛成する。
Of course, I agree with that proposal.
Example sentences
もちろん、会議の資料は今日中にお送りします。
Of course, I will send the meeting materials by the end of today.
もちろん、申込書はオンラインで提出できます。
Of course, the application form can be submitted online.
もちろん、明日の朝までに図書館へ本を返します。
Of course, I will return the book to the library by tomorrow morning.
もちろん、駅までお迎