noun
scale leaf
Botanical term for a reduced, often protective leaf, such as those on buds, rhizomes, or bulbs.
タマネギの外側の薄皮は鱗片葉が変化したものです。
The thin outer skin of an onion is a modified scale leaf.
鱗片 means 'scale' in a general sense (fish scale, flake, etc.), while 鱗片葉 specifically refers to a scale-like leaf in botany.
Compound of 鱗片 (scale) + 葉 (leaf). A straightforward technical term.