What is mlu (mean length of utterance) in speech therapy?

The average length of a child's sentences, measured in morphemes (meaningful units). SLPs use MLU to track language development. Higher MLU = more complex language. Example: A child saying "big truck go fast" has an MLU of 4.

📈Developmental Milestones

MLU (Mean Length of Utterance)

What is mlu (mean length of utterance) in speech therapy?

The average length of a child's sentences, measured in morphemes (meaningful units). SLPs use MLU to track language development. Higher MLU = more complex language.

Example

A child saying "big truck go fast" has an MLU of 4.

🔊 Sentences of different lengths

How can I help my child with mlu (mean length of utterance)?

Our interactive books model sentences of increasing length and complexity.

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About this guide: This glossary is designed to help parents understand speech therapy terminology. Definitions are simplified for clarity and informed by resources from the American Speech-Language-Hearing Association (ASHA).

Not medical advice: This information is educational only. For concerns about your child's speech development, consult a licensed speech-language pathologist (SLP).Find an SLP near you →

Learn More From Trusted Sources

ASHA: Speech & Language Development Chart— Official milestones by age
ASHA: Late Blooming or Language Problem?— When to seek help
Identify the Signs— ASHA's early intervention resource

Parents Also Ask

What is MLU and why does it matter?▼

MLU (Mean Length of Utterance) measures the average length of a child's sentences. It's a key indicator of language development. Higher MLU = more complex language. SLPs track MLU to monitor progress and set goals.

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