Since—Ago

Dr. Johnson says of these two adverbs: "Reckoning time toward the present, we use since ; as, 'It is a year since it happened': reckoning from the present, we use ago ; as, 'It is a year ago .' This is not, perhaps, always observed." Dr. Johnson's rule will hardly suffice as a sure guide. Since is often used for ago , but ago never for since . Ago is derived from the participle agone , while since comes from a preposition. We say properly, "not long" or "some time ago [agone]." Since requires a verbal clause after it; as, " Since I saw you"; " Since he was here."