Morpheme

Furthermore, technically, the mean length of utterance is an MLU, and that is not the same thing as words per age.

It's a linguistic measure that you will see on your speech pathology report, if you have one, that bases the average length of a child's utterances on what we call morphemes.

Morphemes also measure complexity, and it is defined as the smallest unit of meaning.

An example of a morpheme would be if I say the word cat, you know that there's one.

If I say the word cats, you know that there's more than one simply by one small unit, which is the S sound at the end of the word.