noun which may take the genitive case particle 'no', noun
Used for physical position (top of a stack, shelf, list) and for age (eldest child). The 'oldest' sense is common in family contexts.
本棚の一番上の棚に辞書がある。
The dictionary is on the top shelf of the bookshelf.
彼は三兄弟の一番上です。
He is the eldest of three brothers.
I put the dictionary on the very top of the bookshelf.
The eldest child is already in high school.
Please put that box on the very top.
Compound of 一番 (number one, most) and 上 (up, above). The 'oldest' sense comes from the idea of being first in birth order.