If you describe something as welcome, you mean that people wanted it and are happy that it has occurred.

If you say that someone is welcome in a particular place, you are encouraging them to go there by telling them that they will be liked and accepted.

If you tell someone that they are welcome to do something, you are encouraging them to do it by telling them that they are allowed to do it.

If you say that someone is welcome to something, you mean that you do not want it yourself because you do not like it and you are very willing for them to have it.

You use welcome in expressions such as welcome home, welcome to Boston, and welcome back when you are greeting someone who has just arrived somewhere.

You say 'You're welcome' to someone who has thanked you for something in order to acknowledge their thanks in a polite way.

A welcome is the act of greeting someone when they arrive somewhere.

The welcome an action, decision, or situation is given is the way people react to it.

If you make someone welcome or make them feel welcome, you make them feel happy and accepted in a new place.

If you welcome someone, you greet them in a friendly way when they arrive somewhere.

If you welcome an action, decision, or situation, you approve of it and are pleased that it has occurred.

If you say that you welcome certain people or actions, you are inviting and encouraging people to do something, for example, to come to a particular place.