Learner's definition of FRACTION
a number (such as ¹/₂ or ³/₄) which indicates that one number is being divided by another
a number (such as 3.323) that consists of a whole number and a decimal
a part or amount of something
a fraction of an inch/second
We've described only a small fraction [=portion] of the available options.
The new program will provide similar benefits at a fraction of the cost (of the old one). [=at much less cost; for much less money]
We can now do the job in a fraction of the time. [=in much less time]