2indexing radical for characters topped by a horizontal-with-dot cap
Tips
usage
亠 is informally called 文字头 or 点横头 — a tiny cap formed by a dot above a horizontal. It is not a real word; you only meet it as the top of characters like 京, 亦, 交, 亡, 立, and 亥.
history
Xinhua simply marks 亠 as 部首用字 (used only as a radical). It has no independent meaning or pronunciation in the modern language; the reading tóu is conventional dictionary shorthand.
Radical
LidKangxi #8
The lid radical. A purely structural cap (dot above horizontal) used to index characters whose top register is a small hat-like element (京, 亡, 交, 亦, 亥). Not a standalone word, but a useful visual hook for grouping otherwise unrelated forms.
