When DS turned two (Jan), he could say: Mumma, dada, yeah, hiya, buh-bye. Thank you was "agg-ooh".
I got him to HV, and mention my concerns over his talking (by two they should have like, 50 words), and they referred him to audiology.
He had that a couple weeks back, and confirmed glue-ear in both ears, so he can't really hear properly, what is said to him, or what he's replying.
He'll have another check in a few months to see if it's cleared.
In just three months, he's come on a long way. Says all of the above, counts to 13, says red, yellow, and blue, "there it is", uh-oh, oh no, oh dear, he sings along with "let it go" (not clearly, but enough to know that's what he's doing), and a few other odds and ends.
15 months is still early hon, and they do things so flippin quickly at this age... One minute, they can't walk a step, next they're running away from you...
Crazy.
I honestly wouldn't worry at all at such a young age xx