subsample

Noun

 * 1) A smaller portion of an original sample, created by trimming, subdividing, splitting or discrete collection of the original sample.
 * 2)  A portion of the original sample that is representative in nature to that of the original sample, thereby assuring equivalency in results from tests and analysis either upon the subsample or the original material, independent of their size.

Verb

 * 1)  To take subsamples from.

Usage notes
Descriptions that refer to 'discrete subsample', 'distinct subsample', 'separate subsample', or 'individual subsample' all refer to a subsample not necessarily representative of the original and which may differ widely in any number of characteristics from that of the original sample.