Two refers to the quantity of 2. Example: I have two apples.
Twice means "two times" which refers to both multiplication and two occurrences. For example: I have twice (two times) the amount of clothes than my sister. OR
I went to the mall twice (two times) today.
Two is a number. Twice is an operator which means multiply by 2. Several is a non-specific number, more than 2 but not very many.
two more
times two
One phrase commonly used to mean twice is "a two-fer".
"Bi-" as a prefix means two or twice. It is used to indicate two or twice the quantity or amount of something.
two fold means twice as much.
2x - 2
It means multiply by two. As in "what is twice 3" that means what is 3x2.
Twice in Math would mean the same as it would anywhere elses. It would mean to do something two times.
It means "twice as much", i.e "doubled".
"Bi-yearly" typically means occurring twice a year or every two years.
Twice a month means that something happens two times in one month, usually on a regular schedule.