Does 'over' include the number?

it means 'more than 20'

No. More equals "greater than" so "over 20" cannot start at 20, but at 21, assuming you're talking whole numbers.

guess he cant read can he ,  another troll with a dumb question . it doesnt include 20 but it includes 20.01 , its greater the 20 even . only an idiot cant work it out , am i right idiot !!!

If you're talking about age then, yes. 'Over 21 welcome.' Means when you hit the 21 st. birthday you can come in. So including the 21st. year.

But for most other things, no." Welcome if you're more than 21". Would mean come in at 22nd birthday.

It does not include 20. 

To include 20, you'd have to say 20 and over. 

Not generally, but it can be inclusive in certain situations, but the inclusion is implied and assumed rather than declared.  The limit is not, strictly speaking, part of the excess so it would not be part of the "more than" range in literal meaning.  20 is not more than 20, not over 20.

''Over 20'' means after your 20th Birthday .. so that includes the year that you are 20.

It depends whether you're talking about age or something else. "Over" means "more than" so in general "over 20" means more than 20. If you're talking about age, like "you have to be over 18 to enter" it includes the number. Probably this is because your age is 18 for a whole year. 18 1/2 is more than 18 but if your age is 18 1/2 you still say you're 18.

Usually yes. If you are over 20 in age, that includes being 20.

But it is ambiguous, so in legal text you would say 20 and over. 

If you say MORE than 20, that would be numbers greater than 20.

Note in mathematics 'greater than' is an inequality so it must be a 

number bigger than 20 (otherwise it would be equal or greater than...)

No, it means every number greater than 20