Several parts combine into one character.

Phonetic-semantic compound: 辶 (walking radical) + 周 (circumference / cycle). The encoded meaning: "moving in a complete cycle" = a week. Originally 周 alone carried the cyclical meaning; later scribes added 辶 to specify "the unit of cyclical movement", giving us today's 週.

Mainland Chinese simplification removes 週 entirely. Instead of 週, simplified Chinese uses just 周 — making this one of the very rare cases where a character is removed rather than simplified in form. So: — 繁體 (Traditional, Hong Kong, Taiwan): 週 for "week". — 新字体 (Japan): 週 — kept the traditional form. — 简体 (Mainland China): 周 (the same 周 that means "circumference") does double duty as both meanings.

Mandarin: zhōu, level 1st tone (using 周 in mainland China). 周末 (zhōumò, weekend), 周日 (zhōurì, Sunday), 一周 (yīzhōu, one week), 周年 (zhōunián, anniversary). Mandarin's spoken word for "week" is 星期 (xīngqī, "star period"), with 周 used in formal/written contexts.

Japanese: on-reading シュウ (shū) is dominant for 週 — 週末 (shūmatsu, weekend), 今週 (konshū, this week), 先週 (senshū, last week), 来週 (raishū, next week), 毎週 (maishū, every week), 一週間 (isshūkan, one week). The full set 先週/今週/来週 is among the foundational time-vocabulary every Japanese learner masters.

Kun-reading is essentially absent — 週 is exclusively on-reading シュウ in Japanese practice.

Memory aid: a journey (辶) around a circle (周) — one full circuit equals a week.