vowels and open vowels according the openness of the mouth. 3)They may be classified into unrounded vowels and rounded vowels according to the shape of the lips. 4)They may be classified into long and short vowels according to the length of the sound. 2.3 Phonology 2.3.1 Phonology and phonetics Phonetics is concerned with the general nature of speech sound while phonology aims to discover how speech sounds in a language form patterns and how these sounds are used to convey meaning in linguistic communication. 2.3.2 Phone,phoneme,and allophone A phone is a phonetic unit or segment.The speech sounds we hear and produce during linguistic communication are all phones. A phoneme is a phonological unit;it is a unit that is of distinctive value.It is an abstract unit.It is not any particular sound,but rather it is represented or realized by a certain phone in a certain phonetic context. The different phones which can represent a phoneme in different phonetic environments are called the allophones of that phoneme.For example,the phoneme// in English can be realized as dark []clear [l],etc.which are allophones of the phoneme / 2.3.3 Phonemic contrast,complementary distribution,and minimal pair If the phonetically similar sounds are two distinctive phonemes,they are said to form a phonemic contrast,e.g./p/and /b/in /pit/and /bit/. If they are allophones of the same phoneme,then they do not distinguish meaning,but complement each other in distribution.For instance,the clear/l/always occurs before a vowel while the dark always occurs between a vowel and a consonant.or at the end of a word.So the allophones are said to be in complementary distribution. When two different forms are identical in every way except for one sound segment which occurs in the same place in the strings,the two sound combinations are said to form a minimal pair.So in English,pil/and bil/are a minimal pair 2.3.4 Some rules in phonology 2.3.4.1 Sequential rules Sequential rules are rules that govern the combination of sound in a particular language. 2.3.42 Assimilation rule The assimilation rule assimilates one sound to another by"copying"a feature of a sequential phoneme,thus making the two phones similar. 8 vowels and open vowels according the openness of the mouth. 3）They may be classified into unrounded vowels and rounded vowels according to the shape of the lips. 4）They may be classified into long and short vowels according to the length of the sound. 2.3 Phonology 2.3.1 Phonology and phonetics Phonetics is concerned with the general nature of speech sound while phonology aims to discover how speech sounds in a language form patterns and how these sounds are used to convey meaning in linguistic communication. 2.3.2 Phone, phoneme, and allophone A phone is a phonetic unit or segment. The speech sounds we hear and produce during linguistic communication are all phones. A phoneme is a phonological unit; it is a unit that is of distinctive value. It is an abstract unit. It is not any particular sound, but rather it is represented or realized by a certain phone in a certain phonetic context. The different phones which can represent a phoneme in different phonetic environments are called the allophones of that phoneme. For example, the phoneme /l/ in English can be realized as dark [ɫ], clear [l], etc. which are allophones of the phoneme /l/. 2.3.3 Phonemic contrast, complementary distribution, and minimal pair If the phonetically similar sounds are two distinctive phonemes, they are said to form a phonemic contrast, e.g. /p/ and /b/ in /pɪt/ and /bɪt/. If they are allophones of the same phoneme, then they do not distinguish meaning, but complement each other in distribution. For instance, the clear /l/ always occurs before a vowel while the dark /ɫ/ always occurs between a vowel and a consonant, or at the end of a word. So the allophones are said to be in complementary distribution. When two different forms are identical in every way except for one sound segment which occurs in the same place in the strings, the two sound combinations are said to form a minimal pair. So in English, pill and bill are a minimal pair. 2.3.4 Some rules in phonology 2.3.4.1 Sequential rules Sequential rules are rules that govern the combination of sound in a particular language. 2.3.4.2 Assimilation rule The assimilation rule assimilates one sound to another by “copying” a feature of a sequential phoneme, thus making the two phones similar