I have 3 children - you child sounds great to me.
first child - said mummy daddy, no, yes, and maybe some animal sounds - but all pretty unclear. Much more interested in running around being a plonker. Didn't start talking till over 2 and then it came like a wave. He was very unclear until he was 4 though. He's in secondary now and the most emotionally intelligent, happy bright child.
second child - talking by 18 months. Doesn't stop talking ever. I mean ever. Much more serious. Will probably be a despot.
third child 19 months - says mummy, daddy, no, yes, woof woof (but more like weird heavy breathing) and good girl. Much more physical than second child.
But at 18 months they all seemed to understand what I was saying and made attempts to communicate - like pointing, moaning, laughing, would follow simple instructions (If I said, get your shoes, or do you want some banana?_
Honestly, at 18 months I wouldn't worry - unless you have other concerns. Wait till nearer 2.