1.InterjectionIt doesn't matter, it's unimportant, it doesn't make any difference."It seems that Doug's coat has gone missing. Oh, well, no matter: we can always buy a new one, now can't we?; "Did you fail your exam?" "Yes, but no matter. I'll just study harder next time.""
2.PrepositionIrrespective of, regardless of, in spite of."As an experienced geologist, he can identify any rock no matter where he finds it.; No matter what the excuse, you must not be late.; We can fix your plumbing no matter the problem.; I'll pick you up at the airport on Friday no matter when your flight arrives."