sahih  (صحيح)

Sound/correct/authentic. Used mainly to refer to hadiths and/or the books they were written in.

The most famous sahih books are Sahih by Bukhari, and Sahih by Muslim. There are 6 recognised sahih books collectivly known as the sihah sitah (six sahihs). These books contain narrations of what Prophet Muhammed (SAW) did or said as well as other details.