Phonology

What is phonology ?

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

 

Phonetics vs. phonology

 

Phonetics deals with the production of speech sounds by humans, often without prior knowledge of the language being spoken. Phonology is about patterns of sounds, especially different patterns of sounds in different languages, or within each language, different patterns of sounds in different positions in words etc. 

Phonology as grammar of phonetic patterns
 The consonant cluster /st/ is OK at the beginning, middle or end of words in English.

• At beginnings of words, /str/ is OK in English, but /ftr/ or /tr/ are not (they are ungrammatical).
• /tr/ is OK in the middle of words, however, e.g. in "ashtray".
• /tr/ is OK at the beginnings of words in German, though, and /ftr/ is OK word-initially in Russian, but not in English or German. 

For example, the glottal stop [] occurs in both English and Arabic BUT ...

In English, at the beginning of a word, [] is a just way of beginning vowels, and does not occur with consonants. In the middle or at the end of a word, [] is one possible pronunciation of /t/ in e.g. "pat" [pa].

In Arabic, // is a consonant sound like any other (/k/, /t/ or whatever): [íktib] "write!", [daíia] "minute (time)", [a] "right"

Phonemes and allophones, or sounds and their variants

The vowels in the English words "cool", "whose" and "moon" are all similar but slightly different. They are three variants or allophones of the /u/ phoneme. The different variants are dependent on the different contexts in which they occur. Likewise, the consonant phoneme /k/ has different variant pronunciations in different contexts. Compare:
 

keep	/kip/	The place of articulation is fronter in the mouth	[k+h]
cart	/kt/	The place of articulation is not so front in the mouth	[kh]
coot	/kut/	The place of articulation is backer, and the lips are rounded	[khw]
seek	/sik/	There is less aspiration than in initial position	[k`]
scoop	/skup/	There is no aspiration after /s/	[k]

These are all examples of variants according to position (contextual variants). There are also variants between speakers and dialects.

source:

https://en.wikipedia.org/wiki/Phonology

http://www.phon.ox.ac.uk/jcoleman/PHONOLOGY1.htm

A Linguistics Primer for Malaysians. Loga Mahesan Baskaran. University of Malay Press. 2005