Complementary distribution: When two or more than two allophones of the same phoneme do not distinguish meaning and occur in different phonetic environments, then the allophones are said to be in complementary distribution. ＊②Free variation: If two sounds occurring in the same environment do not contrast; that’s to say, if the substitution of one for the other does not generate a new word form but merely a different pronunciation of the same word, the two sounds then can be seen as in free variation. ③Phonemic contrast: If the phonetically similar sounds are two distinctive phonemes, e.g. [p] and [b] in “pit” and “bit”, they are said to form a phonemic contrast.