Rarely, twice is used as a noun to mean two times or a double amount, mainly in literature or poetry.
The twice of his effort was needed.
Achieving this twice requires patience.
Twice can show that one thing has double the amount or size of another. It compares two things.
This box is twice as big as that one.
She is twice as tall as her brother.
In medicine or science, twice shows how many times tests or treatments happen. It means they happen two times.
The patient was tested twice for the virus.
Administer the medicine twice a day.
People use twice in expressions to ask someone to be careful or to show the action happened more than once. It means not just one time.
I have told you twice already!
Look twice before you cross the road.
In math, twice means you multiply a number by two. It shows a value is double another.
Twice five equals ten.
The number is twice the original value.
Used figuratively, twice shows something happens more than normal or with greater effort or feeling.
He was twice as nervous before the test.
She worked twice as hard to finish.
