"Wait and see" costs the most.

Most do, and that's exactly the problem — nobody can tell in advance which children will and which won't, and for the ones who don't, time is the thing that matters most. So the answer is both: do the home techniques and get referred. If they catch up, the referral cost you nothing. Waiting lists are often long, so referring early means the wait starts earlier rather than committing you to anything, and it can always be declined later.

Book a hearing test, before anything else. Fluctuating hearing loss from fluid in the middle ear is very common in toddlers and easily missed, precisely because the child appears to hear some of the time so nobody thinks to check — and it directly affects speech development. A history of ear infections makes it more likely rather than less worth testing. The test is quick, painless and available at this age.

Less than understanding, which is generally the stronger predictor and the thing professionals ask about first. Check it honestly: give an instruction without pointing, looking at the object or gesturing, because children read context brilliantly and it's easy to overestimate comprehension. A child who understands well but says little has a different picture from one who doesn't appear to understand.

Two subtractions and one addition. Stop quizzing — "what's this?" and "say ball" are tests, and children reliably go quiet when tested, so comment on whatever they're already looking at instead. Wait longer: adults fill a silence in under a second while a toddler may need five to ten, and many children who seem unresponsive are simply being interrupted. Then repeat back what they said with one word added.

No. Growing up with more than one language does not cause language delay — the myth is widespread and genuinely harmful, because families advised to drop their home language lose the child's richest input and weaken the connection to relatives. Count words across all languages together, and keep speaking whichever you're most fluent and natural in, since that's where the richest language comes from.