break or vacation

休み(やすみ)	Could be anything from a short break to summer vacation – it all depends on the word before it. $$$

休憩(きゅうけい)	Break at work (昼休み is actually a type of きゅうけい） OR break from studying/training. Just long enough to eat some food and stretch – usually 15 minutes to an hour.

休日(きゅうじつ)	A holiday – Christmas, Arbor Day, etc.

休暇(きゅうか)	Long vacation from work (maternity leave, 2-week vacation to Barbados, etc.)