Concept	Definition
Rarefaction	A technique used to compensate for different intensities of sampling in diversity studies.
Subsampling cycle	It consists in the successive random extraction of a given number of items from a sample, lower than the sample size, with or without replacement at each extraction.
Subsampling with replacement	This is based on a situation where an element is randomly extracted from a sample, identified, and then immediately replaced. Therefore, this element can be obtained again in further extractions along the same subsampling cycle.
Subsampling without replacement	All extractions in a subsampling cycle are performed without replacement, so no item may be extracted multiple times in the same cycle.
Downward bias	Inaccuracy in measurement or estimation that underestimates the true value.
Subsampling fraction	Fraction of reads being subsampled from a given sample in a single resampling cycle.
Granularity	Level of resolution at which the data are processed when estimating frequencies from counts.