～杯
～はい · ～hai · JLPT N5 · noun
cup
🍵 Say hai (yes) to another cup: one cup = ippai, two = nihai
杯 is the kanji for a drinking cup, read hai when counting cupfuls or bowlfuls. The sound shifts with the number: ippai (1), nihai (2), sanbai (3). Ippai also means full, so one cupful is literally a full one.
杯 — wood radical 木 + 不 (phonetic)
杯 is a semantic-phonetic compound. The 木 radical signals wood, since ancient cups were carved from wood, while 不 hints at the sound. Originally written 桮, it came to mean any cup or glass regardless of material.