How Kids Develop Grammar Skills: A Guide to Brown’s Morphemes for Parents
Watching your child’s language skills grow is both fascinating and exciting—one day, they’re saying single words, and before you know it, they’re forming little sentences! Did you know we have a good idea of how grammar develops in young kids?
One of the best tools to understand this process is Brown’s Morphemes, a research-based framework that outlines the typical order in which kids pick up grammar skills. Let’s break it down so you can better support your child’s language development in your everyday routine.
What Are Brown’s Morphemes?
Think of Brown’s Morphemes as a roadmap for grammar development. It’s a set of 14 language milestones that children tend to reach in a predictable order as they learn to speak. These include common grammar markers like:
✅ -ing (e.g., “running”, “I eating ‘nana!”)
✅ Plurals (-s) (e.g., “cats”, “Ooo apples!”)
✅ Prepositions (in, on) (e.g., “in box”, “on mine!”)
By understanding these stages, you can track your child’s progress and find easy ways to encourage their growing language skills—without turning it into “extra work” (and as a mom of 2 sons…I’m all for making the most out of what we’re already doing).
Why Should You Care About This?
You don’t need to memorize all 14 morphemes (promise!). But knowing a little about how grammar develops can help you:
✔ Track your child’s progress – See where they’re at and what’s coming next.
✔ Support learning naturally – Use simple, everyday moments to build grammar skills.
✔ Recognize when to seek help – Spot potential delays and get support if needed.
✔ Notice differences in development – If you notice your child is not developing language in this sequential way, your child may not be an analytic language processor (I’ll talk more about this later!).
📏 First…What’s MLU and How Can You Use It?
Mean Length of Utterance (MLU) is a quick way to measure your child’s grammar growth. It tells us the average number of morphemes in a child’s sentences…double wait, what’s a morpheme?!
A morpheme is the smallest unit of meaning in language. Sometimes it’s a whole word (cat, run, happy), and sometimes it’s a word part that adds meaning (-s for plurals, -ing for actions, -ed for past tense). For example:
"Dogs" has two morphemes (dog + -s)
"Jumping" has two morphemes (jump + -ing)
"Mommy’s phone" has three morphemes (Mommy + -’s + phone)
“This seems really complicated!” has six morphemes (This + seem + -s + really + complicate + -ed)
Generally, as kids grow, their sentences get longer and more complex because they start adding more morphemes. Instead of just saying “dog”, they might say “dog running” and then later “The dog is running fast!”—it’s a blast to watch in action!
Want to check your child’s MLU? Here’s how to easily calculate it at home ⬇️ :
🔢 How to Calculate MLU at Home
1️⃣ Write down at least 25, ideally 50 things your child says completely (yes, you can record you and your child playing together and transcribe them later…that’s what most SLPs do!).
2️⃣ Count the total number of words or morphemes in those sentences.
Example: “Mommy running” = 3 morphemes (Mommy + run + -ing)
Example: “I want cookie” = 3 morphemes (I + want + cookie)
3️⃣ Divide the total number of morphemes by the number of sentences (ideally 25-50).
That’s your child’s MLU!
🔍 MLU Benchmarks (Average Sentence Length)
Here’s what’s typical:
| Age | MLU (Average Words/Morphemes Per Sentence) |
|---|---|
| 12-26 months | 1.0-2.0 (Single words, early word combos) |
| 27-30 months | 2.0-2.25 (Adding -ing, in, on, s-plurals) |
| 31-34 months | 2.5-3.0 ('s possessives, irregular past) |
| 35-40 months | 3.5-3.74 (More structured sentences, articles 'a', 'the', regular past tense -ed, third person regular, present tense) |
| 41-46+ months | 4.0+ (Fuller, complex sentences- third person irregular) |
A Quick Look at the Stages of Grammar Development
Here’s a breakdown of key grammar milestones, plus easy ways to support your child at each stage:
🌱 Stage 1: 12-26 Months
💬 What They’re Learning: Simple words & word combinations. You should be hearing your child use at least 1-2 word phrases at this stage. Remember, by 24 months the average child is using 200-300 words! Check out our Free Milestones Guide for more helpful information on what we typically see and when.
📝 Examples:
Nomination: “That dog.”
Recurrence: “More milk.”
Negation: “No night night.”
Action + Agent: “Kat play.”
Action + Object: “Go car.”
Agent + Object: “Mommy dress.”
💁 How to Help
🔹 Point & Name – Always use grammatically correct language, and talk, talk talk. Use self talk and parallel talk whenever you can. Label things around the house (“That’s a dog!”), while reading books, and when exploring your world (“Whoa, a black dog!”.
🔹 More & Again – Use “more” naturally (e.g., “More bubbles?”, “Mmm more milk!”, “Again!” when tickling and modeling for your child how to ask for it to happen “again!”).
🔹 Silly Negation – Playfully say things like, “No bear!” while a teddy bear is doing something mischievous or naughty, the sillier the better.
🚀 Stage 2: 27-30 Months
💬 What They’re Learning: Early grammar like -ing verbs & prepositions (in, on), your child can say many different words!
📝 Examples:
Action words: “Dog running.”
Location words: “In cup.” “On chair.”
S- plurals (regular plurals): “Two dogs,” “All the balls.”
💁 How to Help
🔹 Action Words Everywhere – Narrate daily routines (“Mommy is cooking!”).
🔹 Hide & Seek – Hide toys and say, “In the box!” or “On the table!”
🔹 Sorting Games – Group toys & describe them (“Two cars, three blocks”). Anecdotally, I notice my kids with language delays really struggle with plurals. Use them often so your child gets lots of practice hearing plurals!
🏗 Stage 3: 31-34 Months
💬 What They’re Learning: Possessives, irregular past tense, “to be” verb (is it, was it?)
📝 Examples:
“Mommy’s shoe.”
“I ate it.”
“Is it gone?”
💁 How to Help
🔹 Storytelling with Past Tense – Chat about your day (“We ate lunch. You played outside.”).
🔹 Whose Is It? – Ask about ownership (“Whose hat?” “Mommy’s hat!”, “Is this my cookie?” “Nooo, it’s Jimmy’s cookie!”).
🏠 Stage 4: 35-40 Months
💬 What They’re Learning: Articles (the, a), regular past tense (-ed), third person regular (present tense)
📝 Examples:
“The cake.”
“I walked home.”
“Kitty eats fast!”
💁 How to Help
🔹 Treasure Hunt – Ask your child to find things using “the” (e.g., “Find the spoon!”).
🔹 Act It Out – Use dolls or toys to describe actions (“She walked to bed.”).
🔹 I Spy - Point to a picture and say "I spy with my little eye... someone who walks" and have your child guess who it is based on the verb you used.
🎉 Stage 5: 41-46+ Months
💬 What They’re Learning: More complex sentences & helping verbs (is, has), how to simplify (contract) the ‘to be’ verb.
📝 Examples:
“She has one.”
“I’m playing.”
“She’s here.”
“Mommy’s got milk.”
💁 How to Help
🔹 Guess Who? – Play games while reading a book with pictures, using sentences like, “Can you guess who I’m looking at? He’s running,” or “She’s jumping.”
🔹 Helper Verbs in Play – Encourage “I’m revealing it!” or “We’re cooking” during pretend play.
Signs to Watch For
Every child develops at their own pace, but here are a few signs that may suggest your child could benefit from extra support:
🔴 By 24 months: Not combining two words (e.g., “more juice,” “big truck”).
🔴 By 36 months: Not using early grammar like -ing or plural -s.
🔴 Difficulty being understood by people outside the family.
If you’re concerned, a speech-language pathologist (SLP) can help assess whether your child is on track.
💡 Key Terms
Morphology – How words are built and change (e.g., “cat” → “cats”).
Morpheme – The smallest unit of meaning (e.g., “jumped” = “jump” + “-ed”).
Syntax – How words go together in sentences.
For more helpful speech terms defined check out our blog post all about the jargon!
Final Thoughts
Understanding Brown’s Morphemes can help you support your child’s language naturally—no fancy flashcards needed! Simply talking, playing, and reading together is more than enough to build strong communication skills.
And if you ever have concerns? Trust your gut and reach out for support. You’re doing an amazing job! 💛