Not any thing; no thing. / An absence of anything, including empty space, brightness, darkness, matter, or a vacuum.

Something trifling, or of no consequence or importance. / A trivial remark (especially in the term sweet nothings). / A nobody (insignificant person).

(archaic) Not at all; in no way.

(idiomatic) Easy; simple or straightforward.

plural of nothing

For free. / For no reason, wastefully, or pointlessly

It is easy; it is simple.

only

Used as a polite reply after being thanked

(idiomatic, often followed by but) No alternative; nothing else to be done or to have recourse to.