# Phonology/Introduction
## What is 'phonology'?

Phonology is the study of the mental organization of speech sounds in language, and its relation to other language behaviors.
Languages can differ in the ways that the sound system is organized. For example, languages may differ radically in how stress is assigned. In English, stress may distinguish the meaning of a word (compare record, record), and its location must be memorized as part of the word. However, in Choctaw, stress is often completely predictable: every even-numbered syllable will be stressed (except the last syllable of a word) in specific, but frequent environments. One goal of phonology is to describe the stress systems of different languages. More generally, one goal of phonology is descriptive: to document the kinds of sound patterns that occur in different languages.
Besides describing what occurs in different languages, linguistic theory is also concerned with explanation: why do certain patterns occur over and over again in many different languages, while others appear to be completely impossible, and still others appear to be possible but very rare? Taking stress again as an example, phonologists have documented the following generalizations:
* in many languages, stress always falls in the same position in a word, which is called predictable stress
* if stress is predictable, it always falls on one of the first two syllables, or one of the last three
There is no language, for example, which requires stress to fall on the middle syllable of a word. An explanatory theory of stress should tell us why there are no languages of this type, as well as giving insight into why particular languages behave the way they do. In fact, this question makes up one of the subfields of phonology known as accentual typology.
Another subfield of phonology deals with the issue of what sequences of consonants and vowels are allowed. This is the study of phonotactics -- constraints on what sound sequences are allowed in the words of a language. Example (1), below, illustrates that English and Spanish have different phonotactics.
| (1) | English | Spanish |
| word-medial | ostrich, huskey, raspy | estado, escultor, espam |
| word-initial | state, sculptor, spam | --ungrammatical-- |
| word-final | past, ask, gasp | --ungrammatical-- |
English has many words beginning with consonant clusters of the form /sC/ (where C is any consonant). Spanish does not and cannot have words of this form. What Spanish does have are closely related words (known as cognates) which begin with /esC/ where English has /sC/. These facts suggests that Spanish has a phonotactic restriction against syllables that begin with /sC/. This interpretation makes sense out of the fact that when native Spanish speakers learn English as an adult, they sometimes insert an 'extra' vowel (e.g. speed --> espeed). This mispronunciation makes the English form consistent with the phonotactics of Spanish.
Another major topic is alternations. An alternation occurs when the 'same' word or sound sequence is pronounced differently, depending on the context. For example, in American English, the 't' is pronounced differently in atom than in atomic:
* atom [ˈæɾəm]
* atomic [əˈtʰɐmɪk]
The 't' in 'atom' -- technically an alveolar tap, [ɾ] -- is very weak; in fact, most American English speakers cannot hear the difference between this 't' and the 'd' in 'Adam'. In contrast, the 't' sound in atomic is very strong; it is pronounced with a brief puff of air called aspirations -- technically this sound is an aspirated alveolar stop, [tʰ]. Thus, the 't' in atom alternates between [ɾ] (atom) and [tʰ] (atom-ic). This kind of alternation is especially interesting because [ɾ] and [tʰ] are phonetically very different, and yet most native English speakers do not even notice the difference. But the difference is obvious to native speakers of other languages; for example, the [ɾ] in atom sounds like an 'r' to native Japanese speakers, while the [tʰ] in atomic sounds like an unusually strong 't'.
There are several other major topics in phonology, including prosody and intonation, vowel (and consonant) harmony, process interaction (and opacity), computational phonology, historical phonology, and others. The examples of phonotactics and alternation were chosen to illustrate central and interesting phenomena that phonology seeks to explain.

## Core assumptions

All generative theories assume a fundamental division of labor between information that is stored, and information that is computed dynamically, known as the lexicon and the grammar, respectively:
* lexicon -- mental component that stores arbitrary, unpredictable aspects of the pronunciations of words and other sequences
* grammar -- mental component that enforces systematic aspects of pronunciation that hold throughout a language
The distinction between grammar and lexicon is motivated by the fact that some aspects of pronunciation are systematic throughout an entire language, while others vary idiosyncratically from word to word. An example of the former is that in English, voiceless stops are always aspirated (produced with a puff of air) when they occur immediately before a stressed vowel, e.g. 'cat' [kʰæt]. This property holds throughout the language, rather than varying between words, so it is systematic. Because this generalization holds throughout the entire language, it is best explained by the assumption that speakers possess unconscious generalizations as to licit sound sequences in their language -- a phonological grammar. An additional, interesting fact is that these generalizations can vary from language to language. For example, voiceless stops are not aspirated in Japanese or Spanish. This tells us that some aspects of a language's phonological grammar must be learned (because an infant who is exposed to Japanese learns not to aspirate voiceless stops, while an infant exposed to English learns to aspirate voiceless stops before stressed vowels).
An example of a lexical property is the pronunciation of an individual form. For example, the generic form for a domestic feline (cat) begins with a voiceless velar stop (/k/) in English. In Japanese, the generic form for a domestic feline (neko) begins with a denti-alveolar nasal /n/. Not all words begin with a /k/ in English, or with an /n/ in Japanese. Therefore, the initial consonant of a word is specific to the word, and must be stored in the lexicon.