My dd was almost completely silent for 8 months. She never babbled to us or to her toys, never experimented with sounds. She stopped cooing at about 5 months.
Then on the day she turned 8 months she looked at me as I was about to put her in the tub and said, "Hi Mama!" Since that time (it has been about 5 weeks) she has added a couple of words a week. She says dada and mama to the right person, and says "hi," "bye bye," "duck," "tree," and a few others.
I was really worried that something was wrong because she was so so so quiet. But she was just taking it all in, waiting until she got it just right!
My son followed a more traditional pattern, cooing, then babbling, then getting the words right at around a year or even later, I can't remember. It is amazing how different and special they each are.