「先生」 (sensei) refers to a "teacher." It's also a respectful title used for professionals like doctors, lawyers, or experts. When talking to or about a teacher, you can use "先生" as a standalone title, often without "さん."

「先生(せんせい)」は、学校(がっこう)で教(おし)える人(ひと)や専門的(せんもんてき)な知識(ちしき)を持(も)つ人(ひと)への敬称(けいしょう)です。