Frequency: The word is one of the 700 most common words in English.
1.
If something happens ~, there are two actions or events of the same kind.
He visited me ~ that fall and called me on the telephone often...
Thoroughly brush teeth and gums ~ daily...
ADV: ADV with v, ADV adv, ADV n
2.
You use ~ in expressions such as ~ a day and ~ a week to indicate that two events or actions of the same kind happen in each day or week.
I phoned ~ a day, leaving messages with his wife...
ADV: ADV a n
3.
If one thing is, for example, ~ as big or old as another, the first thing is two times as big or old as the second. People sometimes say that one thing is ~ as good or hard as another when they want to emphasize that the first thing is much better or harder than the second.
The figure of seventy-million pounds was ~ as big as expected.
ADV: ADV as adj/adv
•
Twice is also a predeterminer.
Unemployment in Northern Ireland is ~ the national average...
PREDET: PREDET the n
4.
If you think ~ about doing something, you consider it again and decide not to do it, or decide to do it differently.
She’d better shut her mouth and from now on think ~ before saying stupid things.
PHRASE: V inflects
5.
once or ~: see once
~ over: see over