Several parts combine into one character.

Phonetic-semantic compound: 扌 (hand-radical) + 旨 (intent / purport, providing phonetic value). The encoded meaning: "the part of the hand that points / indicates intent" → finger. Functions as both noun (finger) AND verb (to point at / indicate). Identical across 繁體 / 新字体 / 简体.

Mandarin: zhǐ, dipping 3rd tone. 指 covers finger, pointing, and indicating: 手指 (shǒuzhǐ, finger), 指甲 (zhǐjia, fingernail — neutral final tone), 戒指 (jièzhi, ring — "guard finger"; the everyday word for ring), 指挥 (zhǐhuī, to conduct / direct — used for orchestra conductors AND political/military leaders), 指南 (zhǐnán, "to point south" → guide / compass), 指南针 (zhǐnánzhēn, magnetic compass — Chinese invention!), 指出 (zhǐchū, to point out).

Japanese: on-reading シ (shi) — 指示 (shiji, instruction / direction), 指揮 (shiki, command / orchestra-conducting), 指紋 (shimon, fingerprint), 指南 (shinan, guidance — formal, also the name of various 指南書 guidebooks). Kun-readings: ゆび (yubi, finger) and さ.す (sa.su, to point at). 指輪 (yubiwa, ring — "finger-circle") uses both kun-readings.

Note the everyday verb-noun pair: 指で指す (yubi de sasu, "to point with a finger") uses the SAME character twice, once with each reading — once as noun (ゆび) and once as verb (さす). This double-use of one character with two readings in a single phrase is uniquely Japanese.

The historical 指南車 (shǐnánchē, "south-pointing chariot") was an ancient Chinese mechanical compass — invented around 200 BCE. The compass's name preserves 指 (point) + 南 (south) literally.

Memory aid: hand + purport = the digit that indicates / points.