If you're talking about time, "for", "since", and "ago" can be some of the most painful and awkward words to try to wrap your head around. To make things clearer, today we thought we'd have a go at explaining how each of these words works.
When talking about time, "for" is used to denote a measurement of time. It can be used with pretty much any tense to explain the length of an activity. When you use the word "for", it must be followed by a measurement of time or an expression that refers to a measurement of time. For example...
On Saturday I played football for an hour.
He has lived there for ten years.
We're going on holiday for two weeks.
You can also use expressions like "for ages" and "for a long time".
|The Mona Lisa was painted 500 years ago.|
The word "since" tells us when an event started in the past. Unlike "for", you can't use measurements of time, just points in the past. The word "since" can be used with any date or time, as well as with clauses using the past simple. For example...
He's lived there since 2006.
I've played football since I was a child.
We haven't seen him since yesterday.
We use the word "ago" to count backwards from the present. You can use "ago" with the past simple to explain when events started in reference to the present. When you use it, you must make a reference to the past.
He lived there 5 years ago.
65 million years ago dinosaurs roamed the earth.
I was having breakfast an hour ago.
We hope this has cleared up any confusion you may have concerning "for", "since", and "ago"!