that is completely normal. every child is different. i have 2, a 4 year old and a 16 month old. my first son could talk in 2 to 3 word sentences at a year, but my 16 month old has just really started talking, and it is not near a much as my oldest was saying at just a year.
brayden, my 16 month old, was about 7 months old when he said mama, and then about 9 months when he said dada and byebye, and that was about it until he was about 12 months, then he started adding little words here and there, like no no, and nana. but now he is saying more everyday. he is starting to repeat.
but don't worry at all, some children are even older before they say their first word. a friend was telling me the other day that her nephew had not said a word and he was 2 years old, and one day he just walked in the room and said "can i have some coke". so don't worry he will talk when he is ready. before you know it you won't be able to keep him quiet. if i had a penny for every time my 4 year old said "mamma, what..when...why, etc", i would be rich

remember to enjoy every minute. take care