A reduced or scarcely developed leaf at the start of a plant's life (i.e., cotyledons) or in the early stages of leaf development WordNet 3.0 & Open English WordNet

In plant morphology, a cataphyll is a reduced, small leaf. Wikipedia

In plant morphology, a reduced, small leaf Wikidata

A leaf, sometimes abortive, sometimes persistent, that does not develop into a photosynthetic structure, but instead fulfills protective or storage functions. Examples include cotyledons, bud-scales, glochids, rhizome-scales, and bulb-scales. Wiktionary

A leaf that fulfils protective or storage functions. Wiktionary (translation)