Is the word TWICE an adjective or adverb?

[alkaspeltzar]

Reading in dictionaries, they define it as an adverb which in most cases makes sense.

But how does that work in these examples:

Twice a number is four.

Twice the length is 10 feet

She is twice her age.

Here is seems to be an adjective modifiying a noun. Can someone please explain? THanks

[bhaisahab]

Reading in dictionaries, they define it as an adverb which in most cases makes sense.

But how does that work in these examples:

Twice a number is four.

Twice the length is 10 feet

She is twice her age.

Here is seems to be an adjective modifiying a noun. Can someone please explain? THanks

twice predeterminer/adverb - definition in British English Dictionary & Thesaurus - Cambridge Dictionary Online

[alkaspeltzar]

twice predeterminer/adverb - definition in British English Dictionary & Thesaurus - Cambridge Dictionary Online

SO not to ask a stupid question, but a predeterminer is basically just an adjective right?

I read this:
predeterminer (plural predeterminers)
1.(grammar) The function of a phrase that precedes a determiner in a noun phrase and modifies the head noun.

Sounds like it is an adjective, that can be infront of others at times, and yet modify the main noun in a noun phrase
Thanks for the help

[philo2009]

Adjective. It means 'multiplied by 2'.