"Certainly"是英语中表示"当然、无疑、确实"等意思的副词。它的来源是源自中世纪拉丁语"certus"，意为"确实的、确切的"。
例句：
"Certainly, I'll be there on time."（当然，我会准时到的）
"Would you pke another cup of coffee?” “Certainly.”（你想再来一杯咖啡吗？”“当然。”）
"Is it certain that he will win the race?" “Certainly.”（他一定会赢得比赛吗？”“当然。”）