Which concept refers to the study of small sound units in spoken language?

The study of small sound units in spoken language is referred to as phonology. This concept encompasses how these sound units are organized and how they interact within particular linguistic systems. Phonology investigates patterns of sounds, including aspects such as intonation, stress, and the rules that govern how sounds function in particular languages.

In contrast, the other concepts address different areas of linguistic study. Morphology looks at the structure of words and how they are formed from smaller meaning units called morphemes. Syntax refers to the rules and principles that govern sentence structure and the arrangement of words in a sentence. Phonetics, while also concerned with sounds, focuses specifically on the physical properties of these sounds – such as their articulation, acoustic properties, and how they are perceived – rather than their functional roles within a language. Thus, phonology is the correct choice because it specifically deals with sound patterns and systems in language.