Expressing Restriction

"Only" as restrictive

Words like "only" are RESTRICTIVE in the sense that they combine negative meaning with the idea of exception:

“He only knew one answer.” (=’he knew nothing but one answer’) 

“Only my brother knows my secret.” (= ‘no one except my brother…’)

"Only" for amounts and degrees

If we have an expression of amount and degree, then only means ‘no more than…’:

“Only a few people came to her wedding" (=’no more than a few…’).

“I know this subject only slightly.” (=’… no more than slightly’)

“He didn’t buy the car from me; he only borrowed it from me." (= ‘… he did no more than borrowing it from me’)

Synonyms for "only"

There are other words with a similar meaning to only, like just,  merely, simply.

When we’re talking about time and timing, the restrictive meaning of only can still be applied, in a slightly different way:

“I’ve heard your news only last week." (=’no earlier than’, or ‘as late as…’)

Contrast between "only" and "even"

However, note that there is a contrast between only and even:

“Only my coat was wet." (=’that and nothing else’).

"Even my underclothes were soaked." (= ‘That as well as everything else’)