Rabbi Eliezer says: the heifer is no more than one year old and the cow no more than two years old. But the sages ruled: the heifer may be even two years old and the red cow even three or four years old. Rabbi Meir says: even five years old, though she is old. But they did not wait with it so long since it might in the meantime grow some black hairs and [thus] become invalid. Rabbi Joshua said: I only heard of [a cow] that was three years old [shelashit]. They said to him: What does "shelashit" mean? He replied: thus have I heard it without any explanation. Ben Azzai said: I will explain: if you say "shelishit" the meaning is ‘the third’ in number to others, but when you say "shelashit" the meaning is one that is three years old. Similarly they said a vineyard that is "revai." They said to him: what does "revai" mean? He replied: thus have I heard it without any explanation. Ben Azzai said: I will explain: if you say "revii" the meaning is the fourth in number to others, but when you say "revai" the meaning is one that is four years old. Similarly it was ruled: if a man ate in an afflicted house half a loaf, three of which can be made from a kav, he becomes unclean. They said to him: say rather "eighteen of which are made of a se'ah." He replied: thus have I heard it without any explanation. Ben Azzai said: I will explain: when you say, three of which are made of a kav it would not contain hallah, but if you say, eighteen of which are made of a se'ah, it has been reduced by its hallah.