粗心
cū xīn · HSK 4
careless
粗心 = 粗 (coarse/rough) + 心 (heart/mind) → a rough mind
In Chinese, 心 (heart) often stands in for mind or attention. A coarse, unrefined mind misses details — so 粗心 means careless or thoughtless. Compare 细心 (xì xīn), fine-hearted, which means attentive.
粗 — rice 米 + crude/rough 且
A semantic-phonetic compound. The left 米 (rice) hints at the meaning, since unhulled or coarsely milled rice is rough and grainy. The right 且 supplies the sound. From 'coarse rice' the meaning extended to 'thick, rough, crude' in general.
心 — pictograph of a heart with chambers and aorta
心 is a pictograph showing a stylized heart, with strokes representing the organ's chambers and the aorta at the top. Originally meaning the physical heart, it broadened to cover mind, feelings, and intentions, since ancient Chinese thought located thinking and emotion in the heart.