limit vs level best

limit and level best both are nouns.

Word	Noun	Adjective	Verb	Adverb
limit	Yes	No	Yes	No
level best	Yes	No	No	No

As nouns, level best is a hyponym of limit; that is, level best is a word with a more specific, narrower meaning than limit:

limit (noun)	level best (noun)
the greatest possible degree of something	the greatest possible degree
the boundary of a specific area
as far as something can go
the greatest amount of something that is possible or allowed
the mathematical value toward which a function goes as the independent variable approaches infinity
final or latest limiting point

limit (verb)	level best (verb)
restrict or confine within limits
place limits on (extent or amount or access)
decide upon or fix definitely