As a Noun:
1. Something which is not very important. English = trifle, triviality.
As a Verb or Adjective:
1. To be very unimportant and not worth attention. English = (be) nothing, (be) trivial, (be) trifling, (be) insignificant.
2. To do nothing at all, usually because you are lazy or uninterested.
Interactive:
1. Used alone in response from your addressee to repeat something you have said to mean that you won't bother because what you said was not very important. English = 'It's nothing!', 'Forget it!', and so on.
2. Used alone to deny that you have done or said something. English = 'I haven't done a thing!', 'I've done nothing!', 'I didn't say anything at all!', and so on.
As Modifier:
1. Used next to a verb or adjective to negate it, i.e., to mean that the action does not happen, or that something does not have that quality. English = not, don't, doesn't, didn't.