MLU (mean length of utterance)
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MLU is the average length of a child's utterances in a language sample, usually counted in morphemes, used to measure language development.
Topic: Speech and language
In plain terms
To find MLU, an SLP collects a sample of at least 50 utterances, counts morphemes in each ("dogs" is two: dog and -s), and divides the total morphemes by the number of utterances. MLU grows steadily in early childhood and is most useful for younger children, up to an MLU of about 4 or 5. After that, sentence complexity matters more than length.
How it shows up in an IEP
MLU can be a baseline and progress measure for expressive language goals, taken from comparable samples, such as play with the same toys.
Example
A 4-year-old's 50-utterance sample has 115 morphemes, for an MLU of 2.3. The goal targets an MLU of 3.5 in play-based samples by the annual review.
Related terms
- Language sampleA language sample is a recording of a student's natural talk, transcribed and analyzed to measure everyday language skills.
- Expressive languageExpressive language is the ability to put thoughts into words and sentences to communicate, through speech, sign, writing or AAC.
- SyntaxSyntax is the set of rules for combining words into phrases and sentences, including word order and sentence structure.
- MorphologyMorphology is the study of morphemes, the smallest units of meaning in words, such as roots, prefixes and suffixes.
On IEP Atlas
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