Several parts combine into one character.

Phonetic-semantic compound: 艹 (grass / plant radical) + 采 (to pluck / harvest by hand, providing phonetic value). The encoded meaning: "the plants you pick to eat" → vegetables. Identical across 繁體 / 新字体 / 简体.

Mandarin meaning expansion: in modern Mandarin, 菜 dramatically generalized from "vegetable" to "any prepared dish / cuisine". 中国菜 (Zhōngguó cài) doesn't mean "Chinese vegetable" — it means "Chinese cuisine". 川菜 (Chuāncài) is Sichuan cuisine; 粤菜 (Yuècài) is Cantonese cuisine. 菜单 (càidān, "vegetable list" → menu) — every restaurant has one. So when ordering Chinese food, 菜 is your central word.

Mandarin: cài, falling 4th tone. 菜 (cài, dish / cuisine / vegetable), 蔬菜 (shūcài, vegetables — formal term), 白菜 (báicài, bok choy / Napa cabbage — most basic Chinese vegetable), 菠菜 (bōcài, spinach), 韭菜 (jiǔcài, chives — also a tech-stock slang for retail investors who get harvested by markets), 菜鸟 (càiniǎo, beginner / noob — "vegetable bird", modern slang).

Japanese: on-reading サイ (sai) — 野菜 (yasai, vegetables — most common everyday word), 菜食 (saishoku, vegetarian diet), 菜食主義者 (saishoku shugisha, vegetarian — formal term), 山菜 (sansai, mountain vegetables / wild edibles — culinary term in regional Japanese cuisine), 惣菜 (sōzai, side dish / prepared deli food — Japanese supermarket section name). Kun-reading な (na) survives in 菜の花 (na no hana, rapeseed flower / canola — yellow blossoms that signal Japanese spring), 青菜 (aona, leafy greens), 白菜 (hakusai, Chinese cabbage — common ingredient).

The Japanese 菜の花 (nanohana, canola/rapeseed flower) is a beloved spring symbol in Japanese poetry and visual culture — fields of yellow rapeseed flowers anchor the spring landscape vocabulary.

Memory aid: grass + plucking = the plants you pick to eat → vegetables / dishes / cuisine.