1. the round yellow center of an egg   yoke   yolk   2. board on which artist mixes colors   palate   palette   3. muddy; unclear   turbid   turgid   4. writing or typing materials   stationery   stationary   5. principle or lesson in right behavior   morale   moral   6. a general rule, belief or truth   principle   principal   7. thing required as a precondition   prerequisite   perquisite