to fold in two;  to fold double;  to double
To fold a newspaper in two;  to fold a newspaper double
To fold a blanket double for extra warmth;  to double a blanket (over) for extra warmth
double;  twofold;  twice
A double helping
The new bleach with double strength for killing germs
I'm 40 years old, but he is only twenty - My age is double his/I am twice his age/I am double his age
She spends double what she earns
We need double the amount they have
I'm sure your salary will double this month;  I'm sure your salary will increase twofold this month
He's paid double for the same job
A twofold increase
The car's performance is twice as good since the engine's been tuned
She did twice as much work as me
I'd like twice as much/many;  I'd like as much/many again
This room is twice as long as that one;  this room is twice longer than that one;  this room is twice the length of that one