The collection of one or more increments or units initially taken from a population. The portions may be either combined (composited or bulked sample) or kept separate (gross sample). If combined and mixed to homogeneity, it is a blended bulk sample. The term 'bulk sample' is commonly used in the sampling literature as the sample formed by combining increments. The term is ambiguous since it could also mean a sample from a bulk lot and it does not indicate whether the increments or units are kept separate or combined. Such use should be discouraged because less ambiguous alternative terms (composite sample, aggregate sample) are available. 'Lot sample' and 'batch sample' have also been used for this concept, but they are self limiting terms. The use of 'primary' in this sense is not meant to imply the necessity for multistage sampling.
PAC, 1990, 62, 1193. 'Nomenclature for sampling in analytical chemistry (Recommendations 1990)' on page 1205 (https://doi.org/10.1351/pac199062061193)