When other children the same age are speaking in sentences and yours is still on a handful of words, most parents swing between two thoughts: "it is just a slight delay, let us wait" and "should we not be at a clinic already?". This article will not make that decision for you. What it will do is set out, from public sources, which reference points to use and in what order to proceed.

The line between waiting and checking

Language development varies enormously between children, so there is no single rule of the form "if a child cannot talk by month X, something is wrong". There are, however, reference points that come up repeatedly in clinical practice and research.

A "late talker" is a child whose early expressive language is delayed even though there is no clear physical, emotional or cognitive impairment. The operational definition most often used is a child aged two to three with fewer than 50 expressive words, or who does not produce two-word combinations ("mummy water", "daddy go"). Scoring below the tenth percentile for expressive language on a standardised test is also cited.

What matters here is not the vocabulary count but the gap between understanding and expression. If a child says little but follows instructions well, points at things, makes eye contact and interacts actively, then watching and waiting is a reasonable option. If, on the other hand, the child rarely responds to their own name, does not point, and holds eye contact only briefly, it is better to bring the check forward regardless of how many words they have.

Start with the national check-up you are already entitled to

Before spending money on anything else, there is a tool you already have: the infant and toddler health check-up run by the National Health Insurance Service. Health and dental check-ups are publicly funded from 14 days to 71 months of age, and the Korean Developmental Screening Test for Infants and Children (K-DST) sits inside that programme.

The starting point is widely misunderstood, though. Developmental screening begins at the third check-up (9–12 months). The first (14–35 days) and the second (4–6 months) do not include it. That is why parents so often say, "we went to every check-up, but development never came up".

K-DST looks at gross motor skills, fine motor skills, cognition, language, social skills and self-help. The self-help section is added from the 18-month form onwards. Because each area is scored separately, the result sheet shows whether language alone is low or several areas are low together. That distinction is a practical clue as to where to go next.

Read the four possible results as four different things

This is where most is missed. A K-DST result falls into one of four bands: ahead of peers, at peer level, follow-up testing required, and in-depth assessment recommended.

"Follow-up testing required" is less a problem right now than a signal to look again at the next check-up. "In-depth assessment recommended" is different. It means the screening alone cannot settle the question and the child should be referred for a full assessment; at that point a referral to the relevant service is made. Screening is exactly that — a filter, not a diagnosis. Treating an "in-depth assessment recommended" result as "it was only the screening" means letting one chance to find out go past.

What you can do at home in the meantime

The language environment keeps running while you work through the process. Several things need no special equipment at all.

• Describe more, question less. Repeating "what is this?" puts the child in a test. Putting words on whatever they are already looking at — "a red apple, it's round" — increases the input instead.
• Give a short utterance back one step longer. If the child says "water", expand it to "do you want to drink water?".
• Build in waiting time. Pausing two or three seconds before handing over what the child wants creates an opening for them to vocalise.
• Cut screen time. One-way sound exposure does not substitute for back-and-forth interaction.

That said, if these do not produce improvement, it does not mean the parents did not try hard enough. Language delay has many causes, and a good number of them sit outside anything a family can control. Other articles in Early Development return to the same principle.

In summary

The order is simple. First, use the reference points — 50 expressive words and two-word combinations — to gauge where the child is now. Second, read the K-DST result from the check-up you are already attending, area by area. Third, if it says "in-depth assessment recommended", move to a full assessment rather than putting it off. Following those three steps alone keeps you out of the position of deciding whether to wait on instinct.