This is the 3866th most frequent Japanese word.
ウロコ
"ウロコ" means "scale" (as in fish or reptile scales).
The word ウロコ is used here to refer to the literal scales of a fish.
魚の体にはウロコがたくさんあります。
There are many scales on a fish's body.
ウロコ is described as a reflective component in this sentence, emphasizing its physical characteristics.
その魚のウロコは太陽の光を反射して輝いています。
The scales of that fish are reflecting sunlight and shining.
ウロコ is used in a scientific context to refer to the scales' fossilized remains.