Language is a complex system. The mastery of a language starts shortly after birth but continues throughout childhood until a child attains adult-like speech. Today, developmental psychologists know much about how a child begins to learn language, yet due to the complexity of learning a language, the separate parts of learning to speak are broken up into phonology, or speech; lexicon, or vocabulary; grammar; and expression.
Speech begins even before an infant has learned her first words. Around 3 months of age, an infant begins to play with the sounds her mouth can make. Over the course of several months, these sounds become native-language-like sounds -- words that you could write down but not understand such as “jojo” or “dak.” In fact, according to Erika Hoff, author of "Language Development," many parents have trouble distinguishing these pseudo-words from a baby's first words, but the difference becomes clear somewhere in the first year when these sounds turn into true words and higher level speech begins. Only after several years -- around six to eight -- does a child fully master all the sounds of her native language and pronounce every word correctly.
While many parents consider a child’s first word the first and most important stepping stone in learning words, it is actually the second step. At approximately 3 months of age, an infant can already recognize his own name. The first word, on the other hand, does not come until around 1 year old. It may seem strange that most children’s first words are not their own names, but once you consider that a baby has little need to call out his own name, you realize how much sense it makes. About halfway to age 2, children learn a massive amount of words. This process, known as the “word spurt” in developmental psychology, leads children to a 50-word vocabulary before 2 years old and a 500-word vocabulary before 3 years old. A child’s vocabulary continues to grow at a rather steady rate for the rest of childhood.
Grammar tends to be the slowest part of language to develop. Only as a child nears 2 years old does she begin combining words in a grammatically correct fashion. At this point, parents can expect a child’s grammar to become increasingly more complex, first with increasingly long word combinations and then with grammatical morphologies, such as adding possessives at the end of people’s names. Sentences like “cookie all wet” and “I watching balloon” are typical of a 2-year-old. As children near 3 years old, they begin using more complex sentence structures, including questions and sentences with negative verbs.
Expression, while faster than grammar in language development, can only come after a child has learned the basic sounds and words of his language. The most basic forms of expression begin when an infant is around 1 year of age. Usually the first signs of expressive abilities in a child are spontaneous attempts at communicating. Pointing at an object and voicing a word -- or something that sounds like a word -- shows that the child knows he has the ability to turn sounds into meanings and that he knows how sounds can communicate ideas to listeners. Expression develops simultaneously with the other parts of speech, allowing a child to improve his conversational skills and overall responsiveness, both of which are usually most apparent to the parents between 2 and 3 years old.