B complex

This term refers to a collective group of vitamins rather than a single chemical entity. In medical and nutritional contexts, it is treated as a singular conceptual unit, often appearing in the phrase "B complex vitamin" or simply "B complex" when referring to a supplement containing multiple B vitamins.

Because it describes a specific biochemical category, it is typically used as an uncountable noun. One does not usually refer to "B complexes" unless discussing different formulations or distinct types of vitamin groupings across different species or products.