Babies are sometimes boring.
If you are horrified, then you have not spent more than three hours solely in the company of a nonverbal baby. But not to worry, reading out loud gives you something to say to babies, and their interest, plus the story, distracts you from feeling like the conversation is one-sided. It's just one more reason to love reading.
And then, eventually, babies become verbal. Baby A has been saying "Dad" since about 9 months, and "Aiti" (Finnish for mom) followed a month later. She inconsistently said a couple of other words, and babbles all day long. (Sometimes people think she is speaking Finnish when she babbles so confidently, so I think I'll start "translating" and they'll never know, haha.)
But very exciting and recent vocabulary additions include: "booo" for what a cow says, "ra!" for what a dog says, and "kukka" (Finnish for flower). These can all be traced back to her bookshelf.
She learned to moo from
Sandra Boynton's Moo, Baa, La La La!
Vasikka ja Muita Maatilan Elaimia (Kirjalito, Calf and Other Farm Animals).
She learned to bark from
Boynton's Doggies, and also from visiting doggies in real life.
And she learned "kukka" from seeing flowers in the yard, but said it for the first time while "reading" to herself Eric Carle's The Tiny Seed.
Unexpectedly, she pointed to a flower, and with intense concentration said, "ku...ka". (Sometimes, it comes out "kakka", and if you speak Finnish, you are already chuckling, because that is Finnish for poop.)
You can also get a better grasp of a baby's understood vocabulary from reading. The first time Baby A intentionally identified a picture in a book when asked "Where is the ____?" was when she pointed to the (human) baby at the end of I Love You As Much... by Laura Krauss Melmed, illustrated by Henri Sorensen.
What fun vocabulary practice have you had with babies and their books?