Children use different semantic functions to express ideas. This is evident in single word utterances known holophrases. A holophrase is a single word – used by infants up to the age of 2;00 years – which has the force of a whole phrase which would typically be made up of several (adult) words. Beyond the so-called One Word Stage, children relate different semantic categories to create meaningful, longer utterances.

Human language is a complex communication system that allows the generation of infinitely many different messages by combining the basic sounds (phonemes) into words, and combining the words into larger complex utterances. The way the sounds combine is governed by phonological rules, and the way the words combine is governed by syntactic rules. Human language is, therefore, generative and demonstrates duality of patterning. This article explains these concepts.

Morphemes combine to form words within one of nine word classes. Not all morphemes have the same function. Some are derivational morphemes and some inflexional morphemes. They are acquired in an orderly manner and reduce ambiguity in communication.

What is duality in language? What is language productivity? The term duality refers to the organization of language at two levels: primary level units and secondary level elements. This key property enables productivity in language – the ability to construct an infinite set of new and meaningful utterances.

Is there a critical period? It has been suggested that there is a critical period for children…

Language use refers to the reasons why people communicate – the function of language. In addition it refers to how people both understand and choose from among alternative linguistic forms in order to reach their goals – the context of language. Language use is akin to pragmatics.

Language form refers to the surface features of language and how these are arranged according to the grammar of the language. As a means of connecting sound with meaning, it incorporates morphology, syntax and phonology.

Language content refers to the topics and ideas that are encoded in linguistic messages. We all talk about the same things: objects, relationships between objects, and relationships between events. Content is, therefore, general and independent of any particular context. In contrast, topic is variable and changes with age, as well as culture. Language content is akin to semantics.