yolk: nutritive material of an ovum stored for the nutrition of an embryo (especially the yellow mass of a bird or reptile egg)
food: any substance that can be metabolized by an animal to give energy and build tissue
strike: (baseball) a pitch that the batter swings at and misses, or that the batter hits into foul territory, or that the batter does not swing at but the umpire judges to be in the area over home plate and between the batter's knees and shoulders