Collocations for fraction - noun

large, significant, sizeable, substantial
mere, small, tiny
A mere fraction of available wind energy is currently utilized.

fraction of
Why not grow your own fruit at a fraction of the price?

just a fraction, only a fraction
The average income is high, though many people earn just a fraction of that average.

vulgar (BrE)
decimal
improper
11/8 is an improper fraction, equivalent to one and three eighths.

express sth as
Express 25% as a fraction.