Yesterday, as I was feeding my five-month-old son, he looked up at me and said "Mama". He did it again while we were playing, looked right at me and said "Mama." His cries now tend to sound like "Ma! mamamamamama."
I admit, these "Mama"s are usually followed by a string of "Ga Ga Ga Ba Wa Goo Grrrngg" and other noises that could be interpreted to mean any word in the English language (or any other language for that matter). So whether or not William actually knows the meaning of the word "Mama" or whether he is just exercising his vocal cords is unclear.
I, of course, choose to believe that he says "Mama" because he loves his Mommy. It makes me feel all happy and cuddly inside.