快捷
kuài jié · HSK 7
quick
🐆 快捷 = 快 (fast) + 捷 (swift/nimble) — two fast-words doubled up
快 means fast or quick; 捷 means swift, nimble, or a swift victory. Stacking the two synonyms makes 快捷, the speedy, agile kind of quick used for shortcuts and fast service.
快 — heart radical 忄 + 夬 (phonetic)
快 is a semantic-phonetic compound. The heart radical 忄 carries the meaning, since the original sense referred to a feeling of pleasure or delight. The right side 夬 supplies the sound. The meaning later extended from 'pleased' to 'quick, fast', the dominant modern sense.