No matter means it doesnt matter. It is used with who, whose, which, what, when, where and how.
- No matter where you go, I will follow you.
After no matter, we use a present tense with a future meaning.
- You will be welcome no matter when you come.
No matter who and whoever
The conjunctions no matter who/what etc., are used rather like whoever, whatever etc.
- No matter what you say, I wont believe you. (= Whatever you say, I wont believe you.)
- Phone me when you arrive, no matter how late it is. (= Phone me when you arrive, however late it is.)
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