What is MLU

What is MLU – MLU stands for Mean Length of Utterance. It is a key measure used in speech-language pathology to assess a child’s expressive language development by calculating the average number of morphemes (smallest units of meaning) in their spoken sentences.

What MLU Measures

MLU counts morphemes rather than just words. For example:

• “Dog” = 1 morpheme
• “Dogs” = 2 morphemes (dog + plural -s)
• “Running” = 2 morphemes (run + -ing)

Speech therapists collect a language sample from the child and compute the average length of their utterances. This provides an objective indicator of language progress.

Why MLU Matters

MLU helps:

• Track typical language development milestones.
• Identify potential language delays.
• Set therapy goals for increasing sentence length and complexity.
• Monitor progress in children with speech or language disorders.

It is especially useful between ages 18 months and 5 years, when language grows rapidly.

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Typical MLU by Age

• 12-26 months: MLU around 1.0–2.0 (mostly single words to two-word phrases)
• 27-40 months: MLU around 2.0–3.0
• 41-46 months: MLU around 3.0–4.0
• 47+ months: MLU above 4.0 and increasing in complexity

These are general guidelines. Individual variation exists.

How Therapists Calculate MLU

1. Record a spontaneous speech sample (50-100 utterances).
2. Transcribe the sample.
3. Count morphemes in each utterance.
4. Divide total morphemes by the number of utterances.

This yields the child’s average MLU.

Benefits and Uses

• Early intervention: Detects delays before they impact school performance.
• Goal setting: Therapists target specific MLU increases through structured activities.
• Parent-friendly: Helps families understand and support language growth at home.
• Works alongside other assessments for a full picture of communication skills.

FAQ : What is MLU