I think every kid is different. My little sister could sing her ABC's and talk in full sentences with perfect clearness among many other things between 14 and 18 months. And at probably about 18 months (before two, but after one lol) I could tell you all my vouls and when asked a certain letter, could pick it in a pile of cards marked with the ABC's, and would also sing songs and speak sentences clearly. I could also easily read the front of the newspaper by the time I was three.
And my sister was potty trained by 16 months.
However, both of my brothers hardly said a thing until they were two, and weren't potty trained until they were three-ish. My friend's daughter will be two in june and all she does is babble and maybe say two or three not-so-clear words. (although I have a feeling it's because she never takes the binky out of her mouth, but that's just an opinion.) My brothers are just fine though, both smart and never had any trouble speaking once they got started.
Basically I think it just depends on the child, everyone is different, and I have also heard that boys tend to be slower than girls on average. It's really hard to tell if they actually have a problem until later on. I think he's fine though, just give him some time. I wouldn't worry too much over it, at least not for now.
