This chapter integrates linguistic theory with more general concerns of cognitive science. In the context of cognitive science, language is best thought of as a cognitive system within an individual's brain that relates certain aspects of thought to acoustic signals. In order to appreciate the sophistication of the child's achievement in acquiring language, it is useful to examine all the structure associated with a very simple fragment of English such as the phrase "those purple cows". A major line of approach to linguistic combinatoriality, embracing a wide range of theories, is specifically built around the combinatorial properties of linguistic structure. The regular rules of grammar, like words, idioms, and meaningful constructions, are pieces of structure stored in long-term memory. A debate of over twenty years' standing concerns the distinction between regular and irregular morphological forms in language. Most experimental work on sentence processing concerns speech perception.