The key word is just the word you want to teach the sign for, and is usually the word which carries all the meaning in a sentence. The key words are almost always nouns or verbs. Your baby will come to understand the meaning of an entire spoken sentence just from the one key word they know how to sign. As we discussed earlier you aren’t going to sign every word in the sentence anyway, and by that same token, when you say the sentence you’re only going to emphasize that one word, or several words, which are you are going to do the signs for. When you arrive at the word you want to sign, which is usually a noun or verb, pause for a moment or raise the pitch of your voice slightly to emphasis the word. Pausing slightly while saying the key word tells your baby which word it is you are signing by setting it apart from all the other words in the sentence. This is also why we recommend using the word in several different ways and context throughout the day. Eventually your baby discovers the patterns that you are using and separates from this from the meaning.
Above: Baby signing MILK in different contexts.
A sentence that involves “milk” is usually aimed at asking if they would like some, not about if they want to poor it out for themselves, or how milk comes to be available at a supermarket. This is why we boil signing down to the individual key word and don’t need to sign all the other words in the sentence. At least not for your baby. Using complex sentences come a lot later in life. For now we just want a baby to learn a simple “label” for a word so they can identify it. I promise you that once your baby learns the word for MILK, they’ll know that you are asking them if they want some or don’t want some. To a baby, life is pretty simple! Here is an example of how we might sign and emphasize the word MILK. We might say “Do you want MILK? Do you want to drink some MILK? Are you thirsty for some MILK? Each time we arrive at the word “milk” we pause for a second giving us enough time to sign the word in unison with the word. While doing the second sentence we might continue to sign MILK throughout while baby deciphers the pattern. Since MILK is common to each sentence, your baby will figure out that it’s the important word and the word being signed.