Frequency: The word is one of the 3000 most common words in English.
1.
You use ~ to emphasize that something is only what you say and not better, more important, or more exciting.
Michael is now ~ a good friend...
They are offering ~ technical assistance.
= just, simply
ADV: ADV with cl/group, ADV before v emphasis
2.
You use ~ to emphasize that a particular amount or quantity is very small.
The brain accounts for ~ three per cent of body weight.
= only
ADV: ADV amount emphasis
3.
You use not ~ before the less important of two contrasting statements, as a way of emphasizing the more important statement.
The team needs players who want to play cricket for England, not ~ any country that will have them...
PHRASE: PHR with cl/group, PHR before v emphasis