Children's speech and language development follows a typical pattern. For example at first birth day the normal children speak at least one meaningful word, at the age of 2 years they should able to combined two words and at the age of 3years expected to speak in sentences .The deviation in such pattern is considered as delayed speech and language. Early professional help (Speech language therapy) can be very much effective for developing the communication skills and achieving academic goal among such children.
You can consult Speech Language Pathologist (SLP) for detail evaluation.
Give speech language stimulation.(talk to him based on situation more and more)