欢快
huān kuài · HSK 7
cheerful and lighthearted
🎉 欢 joy + 快 quick = joy that moves fast, cheerful and lively
欢 carries the sense of joy and delight; 快 means quick or brisk (and on its own also means happy). Together the brisk, bouncing joy reads as cheerful and lighthearted rather than calm contentment.
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.