② either[aiðə] （英式 ） [i:ðə] （美式） ③ecologist[i'kɔlədʒist] （英式 ） [i'ka:lədʒist]（美式）


The different pronounciation of free variation may be caused by dialect or personal habit,instead of by any distribution rule.
Distribution of Phonemes
1.Contrastive Distribution(对比性分布） If two sound segments occur in the same phonetic environment,and two different words are produced because of them,then the two sound segments are in contrastive distribution. The different segments in a minimal pair are in such distribution. Eg:din , tin

Not all the phones in complementary
distribution are considered to be allophones of the same phoneme:they must be phonetioneme may also have free variation（自由变体）. Free Variation：If two sound segments occur in the same phonetic environment,but still produce the same word,then the two sound segments are the free variation of the same phoneme. Eg:①economics[i:kə'nɔmiks]（英式） [ekə'nɔmiks]（美式） [i:]and [e]are the free variation of the phoneme/i:/.

It is a very important way to induce（归纳） different phonemes of a particular language through analysing contrastive distribution.
plementary Distribution(互补分 布）. When two sounds never occur in the same phonetic environment,thay are in complementary distribution. Allophones of the same phoneme are in such distribution. Eg:spin[spin] pin[phin]

It is also a very important way to conclude different phonemes that are not contrastive in distribution of a particular language through analysing complementary distribution.