since is a preposition that expresses a particular time or moment in the past. It is most commonly used as a preposition followed by a clause or phrase which indicates a point in time to which something else is compared.
1. 'I am amazed at how much has changed since then.'
2. 'It has been five years since we last saw each other.'
3. 'Since when have you been interested in photography?'
common mistakes associated with using since as a preposition include incorrect usage of other parts of speech such as an adjective, adverb or verb. Since can also be confused with the similar sounding word syntax.
As an adverb, 'since' is used to refer to a point in time from which something has continued up to the present or up to another specified point in time.
He left, and I haven't seen him since.
She has been much happier since.
They've been friends ever since they were children.
When used as an adverb, 'since' usually appears at the end of a clause. The adverbial use of 'since' often implies a significant change or event that marks the starting point.
as a conjunction, 'since' is used to indicate a starting point in time or a reason for something. It can introduce both dependent and independent clauses.
I have been working here since 2015.
Since it's raining, we should stay indoors.
She has been feeling unwell since she ate that sandwich.
When 'since' is used to indicate a starting point in time, it is often used with the present perfect tense. Avoid using 'since' to indicate a duration (e.g., 'It has been two years since I last saw her' is correct, but 'It has been since two years I last saw her' is incorrect).