Ohayou gozaimasu means "Good morning." You use this polite greeting when you meet someone in the morning, typically before noon. It's suitable for friends, family, and colleagues. For example, if you meet your teacher in the morning, you can say, "先生、おはようございます！" (Sensei, good morning!).

朝(あさ)に人(ひと)に会(あ)った時(とき)に使(つか)う丁寧(ていねい)な挨拶(あいさつ)です。午前中(ごぜんちゅう)に使(つか)います。「先生(せんせい)、おはようございます！」