My 20 month old DD only says 2-3 words "Hiya" and "Bye", plus "Mumma" (which seems to mean "I want" rather than Mummy).
She communicates by taking you by the hand to where she wants to go and pointing to things she wants, (including her nappy if she has pooed), nodding and shaking her head.
She babbles a lot although only since she was ? about a year old.
She will go and fetch objects like her shoes and doll if asked, and will also put rubbish in the bin (!) so seems to understand a lot.
I have two older children who started to speak between 12-14 months and had no problems at all with language acquisition.
I am not sure whether it is too early to worry or whether it is a case of the sooner the better to go to the doctor and get "in the system" in case there is a problem. Just wondered what others experiences were, if you had a child with a speech problem when did you notice it and seek help?