Frequency: The word is one of the 1500 most common words in English.
1.
You use ~ when mentioning the main reason or thing involved in something.
The stockmarket scandal is refusing to go away, ~ because there’s still no consensus over how it should be dealt with...
The birds live ~ on nectar.
= primarily
ADV: ADV with cl/group, ADV with v
2.
You use ~ when you are referring to a group and stating something that is true of most of it.
The African half of the audience was ~ from Senegal or Mali...
The spacious main bedroom is ~ blue.
= mostly
ADV: ADV with group