Several parts combine into one character.

Compound ideograph: 七 (originally from 七 "to cut", from earlier batch — and the original meaning of 七 was "to cut" before it became the number 7) + 刀 (knife). The encoded meaning: "to cut with a knife". The character preserves the entire etymology of 七 — it shows where 七 came from. The abstract sense "earnest / urgent" (cutting deep into the heart) developed later. Identical across 繁體 / 新字体 / 简体.

Mandarin has TWO tones — another 破音字: — qiē (1st tone): to cut. 切肉 (qiē ròu, slice meat), 切片 (qiēpiàn, slice / cut into slices), 切菜 (qiē cài, cut vegetables). — qiè (4th tone): earnest / pressing / urgent. 亲切 (qīnqiè, warm / affectionate — important social adjective), 一切 (yíqiè, everything / all — extremely high-frequency word), 切实 (qièshí, practical), 急切 (jíqiè, urgent).

Japanese: TWO on-readings. セツ (setsu) is dominant — 親切 (shinsetsu, kind / considerate — one of the most-used positive adjectives in Japanese; calling someone 親切 is a meaningful compliment), 大切 (taisetsu, important / precious — taught in week one of any Japanese class: 大切な人 = important person), 切手 (kitte, postage stamp — note the kun reading). サイ (sai) appears in 一切 (issai, everything). Kun-reading き.る (ki.ru, to cut) is a high-frequency verb — 紙を切る (kami o kiru, cut paper), 電話を切る (denwa o kiru, hang up the phone — "cut the phone").

大切 (taisetsu) — meaning "important / dear / cherished" — is one of the most emotionally weighted Japanese vocabulary words. To call something 大切 is to declare its meaningful place in your life.

Memory aid: knife + cut-mark = the act of cutting, taken to its emotional extreme.