My son 10 months old 有意識地叫 papa, mama. Now 12.5 months old, knows many sound and can follows your voice. But still cannot say an understandable sentence. Sometimes he likes to tell you a story but no know understands. I will reply him "yes" to encourage him to talk even though I do not understand.
You try to talk to him much. I started to sing simple songs to him and pronounced "papa", "mama" and his name to him since he has been one month old. It seemed a game and we both enjoyed this time very much. He always smiled when I spoke to him like this.
My son could not speak clearly when he was 2 years old. Then I send him to nursery school. I could speak clearly 1 month later. Now he is 3-1/2 and he always non-stop speaking after school.
Don't worry. My little girl can say mama when she's 10-11 months old. And then afterwards, she tried very hard to speak. I understand most of them because that's why I taught her. Only until she starts nursery when she's 2 that she can speak properly. And I find her learnt a lot during Easter holiday. Her language skills improved alot. Very cute.
My girl starts walking by herself when she's only 10-11 months olds. Some people said kids who speaks earlier, walks later or vice versa.