Language acquisition is a process that children move through at various rates. A morpheme is considered the basic unit of speech. As a child ages and learns, the lengths of his patterns of speech increase. The mean length of utterance is a measurement that pertains to the way a child uses morphemes and the average length of her speech. Speech therapists use this type of measurement to assess a child's language abilities.

Step 1

Write down 50 to 100 phrases or sentences that a child says. For this example, consider a sample of four: "Give me toy, " "Good girl," " Doggy jumped up," and "Go see Nonna."

Step 2

Count the morphemes in each sentence. Each word is a morpheme. If there is a prefix or suffix on the word, the prefix or suffix is counted as an extra morpheme. Plurals, possessives and contractions also count as individual morphemes. For the phrases in step one, the morphemes are as follows: 3, 2, 4 (suffix "ed") and 3.

Step 3

Add the morphemes from each phrase and divide by the total number of phrases. In this example, you have 12 morphemes and four phrases. Since 12 divided by four is three, three is the average length of utterance.

Step 4

Compare the child's average length of utterance with data for his age level. Speech therapists use standardized morphological development tables to determine if a child is on track for his age.