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Children’s Speech and Language Development

Speech language therapist playing with child and using makaton sign, Auckland NZ

Children’s Speech Development

As children develop, they increase their range and accuracy of sounds. In the early stages of talking, children use many substitutions and patterns to make talking easier. As they develop, their production increases in accuracy and their clarity increases.

How much of what my child says should I be able to understand?

  • At 12-18 months of age, adults should be able to understand approximately 25% of what your child says.
  • At 18-30 months, adults should be able to understand approximately 50% of what your child says.
  • At 30 months, adults should be able to understand approximately 75% of what your child says.
  • At 4 years, adults should be able to understand 100% of what your child says.
Speech Language Therapy Resource Image, Child Talking

Which sounds do children develop at what age?

A study conducted by McLeod and Crowe (2018), looked in depth at children’s speech sound development across 27 languages. Their results showed the following:

  • 2-3 years: p, b, m, d, n, h, t, k, g, w, ng, f, y
  • 4 years: l, j, ch, s, v, sh, z
  • 5 years: r, zh, th (voiced as in the)
  • 6 years: th (voiceless as in thing)

McLeod, S., & Crowe, K. (2018). Children’s Consonant Acquisition in 27 Languages: A Cross-Linguistic Review. American journal of speech-language pathology27(4), 1546-1571.

My child is swapping sounds, is this normal?

When children are learning to talk, tricky sounds and patterns are simplified using a set of patterns. We call these, phonological processes. As children develop, they systematically stop using these processes, and their speech becomes clearer. The ages at which children stop using the processes are outlined below:

  • 3 years: Prevocalic voicing (e.g. bat for pat), stopping /f/ (e.g. bore for four), stopping /s/ (e.g. tea for sea), and word final devoicing (ret for red).
  • 3.3 years: Final consonant deletion (e.g. boo for book).
  • 3.6 years: Fronting (back sounds are produced at the front of the mouth e.g. tar for car), stopping /v/ (e.g. berry for very), and stopping /z/ (e.g. dump for jump).
  • 3.9 years: Consonant harmony (e.g. pup for cup)
  • 4 years: Weak syllable deletion (e.g. bufly for butterfly) and cluster reduction (e.g. tar for star)
  • 4.6 years: Stopping /sh/ (e.g. doe for show), stopping /j/ (e.g. dam for jam), stopping /ch/ (e.g. tease for cheese).
  • 5 years: Gliding (e.g. wed for red, yo for low), stopping th (e.g. dat for that).

Bowen, C. (1998). Developmental phonological disorders. A practical guide for families and teachers. Melbourne: ACER Press.

Grunwell, P. (1997). Natural phonology. In M. Ball & R. Kent (Eds.), The new phonologies: Developments in clinical linguistics. San Deigo, CA: Singular Publishing Group, Inc.

Does my child have a speech delay?

The sounds and ages listed above are not absolute, but a guide as to how speech develops. A Speech-Language Therapist can conduct a thorough evaluation of your child’s speech, taking into consideration their language/s spoken, their percentage accuracy (e.g. do they achieve the target sound some of the time?), and other considerations such as their consistency and rate of speech.

Children’s Language Development

Children’s language development is an incredible thing, and begins at birth (if not before). At three months of age, babies start to develop turn taking skills. For example, the baby may make a sound, the adult responds to the sound and waits… the baby then responds. By around 8 months babies start to understand some words. By the time they are one year old, they may understand up to 50 words.

The following is a very basic outline of language milestones which occur from one year to seven years:

1 year – 1 year, 6 months:


  • Baby understands 50 words
  • Baby follows one step commands


  • Baby can say 50-100 words
  • Baby uses one word at a time
  • Baby uses lots of babble
Speech Language Therapy Resource Image, Child pointing

1 year, 6 months – 2 years:


  • Baby follows two step instructions
  • Baby starts to answer basic questions


  • Baby can say 200-300 words
  • Baby puts two words together (e.g. Daddy car)

2 years – 2 years 6 months


  • Child understands wh questions e.g. who, what?


  • Early grammar is introduced (ing endings, plural s)
  • Child communicates using 1-3 word sentences

2 years, 6 months – 3 years:


  • Child understands “why”, and prepositions “on”, “in”, “under”
  • Child follows three step commands.


  • Child starts to tell basic “stories”
  • Child uses simple sentences.

3 years -3 years, 6 months:


  • Understands colour words.


  • Child has a vocabulary of around 900-1000 words
  • New aspects of grammar are expressed including irregular past tense (e.g. “went”), articles (e.g. “a”) and possessive /s/ (e.g. Mummy’s).
  • Starts to combine sentences together to express ideas.

3 years, 6 months – 4 years:


  • Child understands “when” and “how”.
  • Child understands basic words for sizes and shapes.


  • Complex sentences emerge
  • Child can report on past events, make predictions, play an imaginative role, and demonstrate empathy.

4-5 years:


  • Child understands time concepts e.g. after.
  • Child understands comparatives (e.g. bigger) and superlatives (e.g. biggest)


  • Later grammatical forms are mastered e.g. third person.
  • Child has a vocabulary of around 1,500 – 1,600 words.
  • Child uses complex sentences e.g. When it is my birthday, I get a fairy cake.
  • Child tells stories, but does not include a climax or resolution in the plot.

5-7 years:

  • Child has a vocabulary of around 3,000 – 5,000 words
  • Child tells stories effectively.
  • Child uses correct grammar 90% of the time.

Does My Child have a Language Delay?

If you have concerns regarding your child’s language development, it pays to get them seen by a Speech-Language Therapist as early as possible. The earlier the child receives support for their language delay, the better the outcomes.

What about bilingual children?

Bilingualism does not cause language delays. Children who are bilingual say their first words around the same time as their monolingual peers. Their vocabularies develop at roughly the same rate as monolingual children, however, this may be divided between the two languages (e.g. a 2;0 year old monolingual English speaker may have 200 words in their vocabulary, while a 2;0 year old bilingual English-Mandarin speaker may have 100 words in Mandarin, and 100 words in English) (ASHA, n.d.; Byers-Heinlen & Lew-Williams, 2013).

ASHA. (n.d.). Learning two languages. Retrieved from

Byers-Heinlein, K., & Lew-Williams, C. (2013). Bilingualism in the early years: What the science says. LEARNing Landscapes7(1), 95-111.

Paul, R. (2007). Language disorders from infancy through adolescence: Assessment & intervention (Vol. 324). Elsevier Health Sciences.

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