Longman Dictionary of Contemporary English - since

~1 conjunction (used with the present perfect and the past perfect tenses) 1 at a time after a particular time or event in the past  (In the 12 months since I last wrote to you a lot has happened to me. | I can't have seen him since 1983. | It's been years since I enjoyed myself so much.) 2 during the period of time after a particular time or event in the past  (Since he started that diet he's lost over 20 lbs in weight. | ever since)  (We've been friends ever since we met at school.) 3 used to give the reason for something  (I'll be forty next month, since you ask. | Since you are unable to answer perhaps we should ask someone else.) ~2 prep (used with the present perfect and the past perfect tenses) 1 at a time in the past after a particular time or event  (They haven't met since the wedding last year. | Since the end of the war over a dozen hostages have been released.)  (- compare for1 (8)) 2 for the whole of a long period of time after a particular time or event in the past  (Since the day we met I have known he was not to be trusted. | ever since)  (Ever since the war she's been able to feed a whole family with a few potatoes and eggs.) 3 since when? spoken used in questions to show surprise, anger etc  (Have you checked this bill? Since when does -42 plus -5 service charge come to -48?) ~3 adv (used with the present perfect and the past perfect tenses) 1 at a time in the past after a particular time or event  (He husband died over ten years ago but she has since remarried. | I've since forgotten what our argument was about. | He walked out of that door last Tuesday and no one's seen him since.) 2 for the whole of a long period of time after a particular time or event in the past  (The accident happened four years ago and she has hardly spoken since. | ever since)  (We came to the UK in 1974 and have lived here ever since.) 3 long since if something has long since happened, it happened a long time ago  (I've long since forgiven her for what she did.)  ( USAGE NOTE: SINCE WORD CHOICE since (prep/conj), from, after, from...to/till/until, for Since is mainly used where you want to talk about a state or activity that started at some time in the past and has continued to the time when you are speaking I've been here since ten o'clock this morning. | The place had completely changed since I went there three years ago (NOT It has changed since three years/ three years before). From or after may be used to show the starting points of periods of time where you do not use since. For example I hope they'll be friends from now on (NOT since now on), means I hope they will be friends from now and into the future. She was very unhappy for a while after leaving home (NOT since) means that she was unhappy from a period of time in the past until a later time in the past. From...to/until/till is used where you want to give both ends of a period of time during which some state existed or some activity was being done. This construction can go with most tenses of the v I was here from ten till two. | From 1990 to the present he's had no regular job (NOT since 1990 to the present).). | She works from sunrise until sunset. For is used where you want to give the length of a period of time, but do not need to say exactly when it started or finished. It goes with all tenses of verbs We lived there for a long time. | She's only staying for a week. When you use for with the present perfect tense, it gives a period of time that ends at the time of speaking I've been waiting for two hours (NOT since two hours). In spoken English the for is often left out I've been here two hours. | She's only staying a week. GRAMMAR The point of time with since may be shown by a clause, which may contain a verb in the simple past He's been ill ever since he arrived. The point of time with since may also be shown less exactly, by mentioning a period of time that ended in the past He's been working here since last week/the 60s (= he started at some time during the 60s). | Since I was a kid I've wanted to visit Disney World. A since clause may also itself cover the whole period from a point in the past to the time of speaking Since she's been living here she's made a lot of friends. However, as in all the above examples, the main v in any clause with since usually has to be in one of the perfect tenses. Compare also Yesterday Bobby told me he hadn't eaten since Tuesday (= between Tuesday and yesterday he did not eat anything). Non-perfect tenses are used only in particular situations, for example where you are talking about the length of time itself It's two weeks since I've seen you (NOT ...since I haven't seen you). | It seems like months since you last paid me. Note also Since the car accident she can't walk properly (= she hasn't been able to walk properly). )