When will my baby understand “NO”?

Since my baby is borned, I have been talking to my baby. I believe that they are constantly learning and the earlier we expose them to words and conversation, the earlier they will learn it. When I do not want my baby to do something such as biting me while nursing or screaming, I will tell him "No, no, no" and stop him for performing the act at the same time. He is now 6 months old and he seems to understand. When I said "No, no, no", he will stop.