Language development is a common source of parental worry, partly because the variation between children is enormous and comparison is inevitable.
Knowing roughly what the range looks like, and what the actual warning signs are, helps distinguish normal variation from something worth investigating.
The rough sequence
Timings vary considerably and the sequence is fairly consistent.
Early months: crying differentiates, then cooing, then babbling with repeated consonant sounds.
Around the end of the first year: first recognisable words, though comprehension precedes production by a considerable margin. A child understands far more than they say, throughout early development.
Second year: vocabulary grows gradually and then, for many children, accelerates markedly — sometimes described as a vocabulary spurt, though the evidence for a distinct spurt as opposed to continuous acceleration is debated.
Around two: two-word combinations begin.
Between two and three: sentences lengthen, grammar develops, and intelligibility to strangers improves substantially.
Three to five: complex sentences, narrative, and the sound system largely completes, though some sounds are typically acquired later.
The variation
Worth emphasising because it causes so much anxiety.
The range of normal is wide at every stage. Children who are late talkers frequently catch up entirely, and a substantial proportion of late talkers show typical language by school age without intervention.
Which is reassuring and also complicates things, because it means waiting is sometimes right and sometimes delays help that would have been useful.
Bilingual children are frequently thought to be delayed and generally aren't. Total vocabulary across both languages is typically comparable to monolingual peers, even where vocabulary in each individual language is smaller. Mixing languages within a sentence is normal and not a sign of confusion.
The actual warning signs
These warrant assessment rather than waiting.
No babbling by around a year.
No response to their name, or apparent inconsistency in hearing.
Loss of skills previously acquired — a child who was using words and stops. This warrants prompt attention.
No single words by around eighteen months.
No two-word combinations by around two years.
Speech that is largely unintelligible to unfamiliar adults by around three.
Limited use of gesture — pointing, waving, showing things to people — which is an early communicative behaviour that precedes speech and whose absence is informative.
Concerns about social communication alongside language: limited eye contact, limited interest in interaction, unusual patterns of play.
And parental concern generally. Parents are frequently right, and the cost of an unnecessary assessment is low relative to the cost of a missed one.
Hearing first
The most important practical point. Any concern about language should prompt a hearing check.
Hearing loss, including the fluctuating hearing loss caused by fluid in the middle ear, is a common and treatable cause of language delay. Glue ear is very common in young children and can substantially affect hearing during the period when language is developing.
Newborn screening catches congenital hearing loss and doesn't catch things that develop later.
What parents can do
The interaction, more than any product.
Talk a great deal, about what's happening. Narrating ordinary activity provides language tied to context, which is how words are learned.
Follow their attention. Naming what a child is already looking at is more effective than directing them to something. Attention has to be shared for the word to attach to the object.
Expand rather than correct. A child saying "dog run" gets more from hearing "yes, the dog is running" than from being corrected. Modelling the fuller form works; correction tends to stop the conversation.
Wait. Leaving pauses after asking something gives time to formulate a response. Adults typically wait far less time than young children need.
Reduce background noise. Television on in the background is associated with reduced parent-child talk and reduced child vocalisation, which is one of the clearer findings in this area.
Read together, talking about the pictures rather than reading straight through.
Sing. Songs and rhymes provide repeated, structured language with strong prosody, which supports sound discrimination.
What doesn't help much
Educational videos and applications marketed for language development. Evidence for these producing language gains in young children is weak, and the video deficit means young children learn considerably less from screens than from people.
Flashcards and drilling, which teach labels without the conversational context that builds actual language use.
Waiting because someone said boys talk later. There's a small average difference and it isn't large enough to explain a significant delay.
Getting assessment
Referral routes vary by health system. Speech and language therapy services generally accept referrals from health professionals, and in many places directly from parents.
Earlier assessment is better than later. Intervention when it's needed is more effective early, and if nothing is wrong, that's worth knowing too.
General information only. Concerns about a child's development should be discussed with a qualified healthcare professional.
Dummies and speech
A question that comes up frequently and has a reasonable answer.
Prolonged and frequent dummy use has been associated in some studies with dental effects and with a higher likelihood of certain speech sound difficulties, though the evidence is not conclusive and effect sizes are modest.
The practical concern is straightforward: a child with a dummy in their mouth is vocalising less, and vocalising is practice.
The usual guidance is to limit use to sleep times once a child is past infancy, and to avoid it during periods of play and interaction. That preserves whatever settling benefit it provides while leaving the day free for talking.