In addition to complementary distribution, allophones of a single phoneme sometimes occur in free variation. This means that they may appear in the same phonetic environment but they do not cause difference in meaning. For example, when producing M in the word-final position, English speakers may pronounce it as an unaspirated (j; or they may pronounce it with the lips closed and the sound unreleased. For the latter case, the allophone is represented as an unreleased Thus, the words in (D) may be pronounced in two alternative ways,