It's magic. That moment when you know, without a doubt. that your baby is expressing herself verbally in an understandable way. When you realize that there is a comprehending brain inside that impossibly large, adorable head. I remember distinctly with Thing 1, the first time I heard her use a word in a reproducable way was one October morning when she was 1 year and 2 months old (no doubt she was using words or syllables in meaningful ways prior to this and I was too obtuse to notice). Anyway she was lying on her belly next to the couch in her room, her arm stretched as far as it could go under the couch plaintively calling "nounou nounou nounou". I had suspected for awhile she was using the word nounou to refer to her pacifier and sure enough, there an agonizing few centimeters from the tips of her probing fingers was the wayward pacifier she could not quite reach. So I picked it up, dusted it off (the days of paranoid sterilizing long over by then) and declared nounou her first word. And given that she still sleeps with the nounou (though not the same one) at three and a half years of age, a very appropriate word to signify the beginning of a long love affair. But it was magic to know, with absolute certainty, that she was verbally communicating in a way I could decipher.
The next moment came about a month later in the bath one evening. I had been quizzing her about body parts on and off for the past several months with no discernable success. That evening, all of a sudden... she just knew, knew it all. Out of nowhere, she could point to her head, her arms, her legs, her nose, her eyes and more amazing still she could point to mine meaning not only did she have a vocabulary but she was able to generalize concepts and recognized the difference between self and other. It was simply mind blowing.
Thing 2's magic moment happened tonight. For awhile she has been saying "bah bah bah" when people leave our house or when she leaves the daycare at the end of the day. "Bah", kind of like "bye" said with a string southern accent. The scientist in me, who needs tons of reproducible data before believing, dismissed it as coincidence. Tonight was the tipping point, one of my mommy friends was leaving with her son and sure enough Thing 2 enthusiastically repeated "Bah! Bah! Bah!" at the door and accompanied it with a very definite wave. The first time I noticed this happen (but dismissed it as random) was on Christmas, so... I am backdating her first word to 9.5 months. I now know with certainly that she said "bye" to my family as they were leaving on Christmas. I don't think I will ever be done feeling grateful for the gift of that memory.