The relationships between sounds and meaning are basically arbitrary. Language uses a finite set of elements to create an infinite set of possible sentences. Language consists of sounds, forms and meaning. People use language for a wide variety of purposes. Language use involves many psychological and emotional factors.
Linguistic knowledge includes knowledge of sounds, forms and meaning.
Language ability is innate in humans. Language ability is common to individuals with vastly different levels of intelligence. Language abilities are related to specific areas of the brain. Aphasia studies show how particular areas of the brain relate to language functions. Apart from being a means of communicating, language is fundamental to perception and memory, thinking and behavior.