快適【かいてき】
pleasant, agreeable, comfortable
快速【かいそく】
high speed, rapidity, rapid-service train (not as fast as express), rapid train
快い【こころよい】
pleasant, agreeable, comfortable, refreshing
快晴【かいせい】
clear weather, cloudless weather, good weather
快楽【かいらく】
pleasure, supreme pleasure obtained by freeing oneself from earthly desires
快活【かいかつ】
cheerful, lively, lighthearted