Yes, but mild. Two-year-olds are usually stringing together phrases and short sentences; four-year-olds are starting out on conversations. But kids do develop at different rates, and sometimes they're slow at first and catch up by school age. The fifth or tenth percentile of the population might be that slow to learn to speak; I'm not sure where exactly you would stand--notably slow, but not extremely so, is my guess. If that speech delay is all the kid has, it's usually not a problem, but it is an indicator that there might be a problem somewhere, like a hearing problem or a more general developmental delay, and most docs would probably look into it. If a kid that age is behind but learning steadily, it's usually just something they treat by giving the kid plenty of opportunities to learn, maybe one of those early-childhood programs or maybe just a few sessions with an OT and the parents to teach them how to help the child catch up. Preemies are often behind like that, or kids who've had early illnesses--if they catch up steadily, it's one of those "watch and wait" things. If they're stalled or losing skills, it's more of a serious problem.