SO DD is 14 months old today (crazy!) and she has perfected the words MINE and NO. DS said no no at this age, but MINE? He didnt start that until closer to 2! And of course they go back and forth yelling it at each other. She'll even say it at gymboree when a child walks near her toy! I try to redirect, and ask him to teach her some polite words and he'll say "please" "thank you eva" and then they yelling MINE starts again.
UGH, maybe she'll get it out of her system now ;)