Phonology is a branch of linguistics concerned with the systematic organization of sounds in languages. It has traditionally focused largely on study of the systems of phonemes in particular languages, but it may also cover any linguistic analysis either at a level beneath the word (including syllable, onset and rhyme, articulatory gestures, articulatory features, mora, etc.) or at all levels of language where sound is considered to be structured for conveying linguistic meaning. Phonology also includes the study of equivalent organizational systems in sign languages.

The word phonology (as in the phonology of English) can also refer to the phonological system (sound system) of a given language. This is one of the fundamental systems which a language is considered to comprise, like its syntax and its vocabulary.

Phonology is often distinguished from phonetics. While phonetics concerns the physical production, acoustic transmission and perception of the sounds of speech, phonology describes the way sounds function within a given language or across languages to encode meaning. In other words, phonetics belongs to descriptive linguistics, and phonology to theoretical linguistics. Note that this distinction was not always made, particularly before the development of the modern concept of phoneme in the mid 20th century. Some subfields of modern phonology have a crossover with phonetics in descriptive disciplines such as psycholinguistics and speech perception, resulting in specific areas like articulatory phonology or laboratory phonology.

Leonard Bernstein ( /ˈbɜrnstaɪn/ US dict: bûrn′·stīn; August 25, 1918 – October 14, 1990) was an American composer, conductor, author, music lecturer and pianist. He was among the first conductors born and educated in the United States of America to receive worldwide acclaim. According to The New York Times, he was "one of the most prodigiously talented and successful musicians in American history."

His fame derived from his long tenure as the music director of the New York Philharmonic, from his conducting of concerts with most of the world's leading orchestras, and from his music for West Side Story, as well as Candide, Wonderful Town, On the Town and his own Mass.

Bernstein was also the first conductor to give numerous television lectures on classical music, starting in 1954 and continuing until his death. In addition, he was a skilled pianist, often conducting piano concertos from the keyboard.

As a composer he wrote in many styles encompassing symphonic and orchestral music, ballet, film and theatre music, choral works, opera, chamber music and pieces for the piano. Many of his works are regularly performed around the world, although none has matched the tremendous popular and commercial success of West Side Story.