Phonology is part of linguistics. Linguistics is the scientific study of language. Phonology is the science that studies the way that sounds (phones) carry meaning in language. Sounds (phones) that do carry meaning in language are called phonemes. Sounds that do not carry meaning in the language are called allophones. Phonology focuses on the study of phonemes, "units of sound (speech) which distinguish one word from another in a particular language." Phonology also includes studies of how words are articulated, or spoken.
The word 'phonology' refers to the sound patterns of a language. Phonology is different from phonetics. Phonology studies how sounds form meaning in language. Phonetics studies how those sounds are formed. Sometimes the studies of phonology and phonetics are combined. This results in more specific areas of study.
Panini was the first person to study phonology in 300 BCE. He created a grammar (a set of language rules) for Sanskrit (an ancient Indian language). He also created a list of the phonemes in Sanskrit. He assigned a symbol to represent each phoneme. These symbols are still used today in phonology.
The first person to use the word "phoneme" was a French linguist (one who studies language) A. Dufriche-Desgenettes. In the 1800s Jan Baudoin gave us the definition of phoneme that we use today. A short time later, Baudouin de Courtenay began the study of phonology. He worked on the theory of phonetic alternations, which predicts changes in the sounds of a language.
One of the best schools of phonology was the Prague school. In 1939 a student of this school, Prince Nikolai Trubetzkoy, published one of the most important studies on phonology. His work was titled Principles of Phonology. Another important person in the Prague school was Roman Jakobson. Roman was the most well-known linguist in the 1900s.
In 1968 Noam Chomsky and Morris Halle published The Sound Pattern of English (SPE). This book described generative phonology. Generative phonology studies how grammar changes how people use language.