There’s a reason your baby’s first word feels magical, whether she was calling out for you or just hoping to get her dinner a little early. Even though it's probably not much longer than three letters, the first word your baby says looms large. But it’s the words that follow that first one that will be the building blocks for her first phrases and sentences and, before you know it, paragraphs full of everything she is thinking! Just talking to her will help her build the vocabulary that will help her to transform into the chatterbox she may turn into. There are also a few specific things that you and your partner can do to help her vocabulary expand.
The words that are going to have the most interest for your baby right now, and the ones she will have the most use for, will be the ones related to her day to day life. It doesn’t matter if the words you use to narrate a trip to the gas station aren’t all that exciting. The important thing about the language your baby is learning now is that it’s teaching her the structure for how words get put together. This means how nouns are pluralized, how verbs are converted, and all of the other things native speakers of a language don't remember having to actually learn, because learning them happens so young. Instead, these parts of speech are the pieces of what is going to 'sound right' to your baby as she grows. your baby is going to learn the basic rules of grammar long before she learns the words to describe them. The words you say to and around her basis for what she thinks language should sound like.
This doesn’t mean you need to walk around with a running monologue going, though, especially if you don't feel comfortable with that. What you’re doing is having a conversation with your baby, even if she isn’t using many words on her side yet. Asking her questions and waiting a moment for her response, and then replying to it, even if it only comes in the form of a gurgle, babble, or significant look, is a great way to keep her engaged in talking to you. Another way is to talk to her about the things she is interested in. Even if she isn’t quite up to telling you what those things are in words yet, you may be able to work out which things are catching her attention just by following where she looks the most often.
A study published in 2013 by Erica Cartmill of the University of Chicago suggests that the children who pick up the most language from their parents aren’t necessarily the ones who hear the most words from their parents. Rather, they are the ones who have parents who use the most expressive gesturing and body language to help their children make the connection between the word they’re saying and the object in the world that it corresponds to. Hearing words is vitally important to young children, but having something to connect those words to is crucial as well. You can help babies make these connections by actions like making eye contact, pointing, and more involved hand gesturing (think "itsy-bitsy spider").