Pictograph: a bird settling into its nest. The encoded reasoning is poetic — at sunset, birds return to their nests; that direction is "west". The ancient Chinese defined cardinal directions partly through bird behavior, partly through sunlight. Identical across 繁體 / 新字体 / 简体.

西 carries strong "the West / foreign" connotations in modern usage — the way the West-East axis carries cultural meaning everywhere. 西方 (xīfāng / seihō / 서방) means both literal "west" and metaphorically "the Western world".

Mandarin: xī, level 1st tone. 西方 (xīfāng, the West / Western), 西瓜 (xīguā, watermelon — historically "western melon", introduced to China from Central Asia along the Silk Road), 西安 (Xī'ān, Xi'an — China's ancient capital, "Western Peace"), 东西 (dōngxi, "thing" — the curious east-west compound from previous entry), 西部 (xībù, western part), 中西 (zhōng-xī, Chinese-Western — used for cuisine, medicine, etc.).

Japanese: TWO on-readings. セイ (sei) is dominant — 西洋 (Seiyō, the West / Occident), 西暦 (seireki, Western calendar / AD year). サイ (sai) appears in 関西 (Kansai, the Kansai region — Osaka/Kyoto/Kobe area, contrasting with 関東 Kantō). The Kansai/Kantō distinction is fundamental to Japanese regional identity, food culture, comedy, and dialect. Kun-reading にし (nishi) is the everyday word — 西 (nishi, west), 西日本 (nishi-Nihon, western Japan), 西口 (nishiguchi, west entrance).

The Buddhist 西方浄土 (Saihō Jōdo, "Western Pure Land") is a major Mahayana Buddhist concept — paradise in the west, where Amida Buddha resides.

Memory aid: a bird returning to its nest as the sun sets — the western direction.