盲

Bottom eye radical — pictograph of a human eye stood on end (rotated from the original horizontal eye-shape for vertical script). The indexing radical, putting 盲 in the seeing family with 眼 eye, 看 look, 睡 sleep. Eyes lost = blind: 盲人 blind person, 文盲 illiterate ("text-blind"), 色盲 colour-blind.

Top 亡 supplies the sound — wáng drifting to máng with regular w/m nasal alternation. 亡 also adds strong semantic flavour: loss, absence, perishing. With 目 below the picture is "lost eyes" — blindness. Same phonetic: 忙 busy, 茫 vast, 芒 awn.