allophones are said to be complementary. The allophones then complement each other, and one of them is not used in a situation in which the usage of another is standard. For complementary allophones, each allophone is used in a specific phonetic context and may be involved in a phonological process. In other cases, the speaker can freely select from free-variant allophones on personal habit or preference, but free-variant allophones are still selected in the specific context, not the other way around. Another example of an allophone is assimilation, in which a phoneme is to sound more like another phoneme. One example of assimilation is consonant voicing and devoicing, in which voiceless consonants are voiced before and after voiced consonants, and voiced consonants are devoiced before and after voiceless consonants. Allotone An allotone is a tonic allophone, such as the neutral tone in Standard Mandarin. Examples English There are many allophonic processes in English: lack of plosion, nasal plosion, partial devoicing of sonorants, complete devoicing of sonorants, partial devoicing of obstruents, lengthening and shortening vowels, and retraction. Aspiration: In English, a voiceless plosive is aspirated (has a strong explosion of breath) if it is at the beginning of the first or a stressed syllable in a word. For example, as in pin and as in spin are allophones for the phoneme because they cannot distinguish words (in fact, they occur in complementary distribution). English-speakers treat them as the same sound, but they are different: the first is aspirated and the second is unaspirated (plain). Many languages treat the two phones differently. Nasal plosion: In English, a plosive () has nasal plosion if it is followed by a nasal, whether within a word or across a word boundary. Partial devoicing of sonorants: In English, sonorants () are partially devoiced after a voiceless sound in the same syllable. Complete devoicing of sonorants: In English, a sonorant is completely devoiced after an aspirated plosive (). Partial devoicing of obstruents: In English, a voiced obstruent is partially devoiced next to a pause or next to a voiceless sound within a word or across a word boundary. Retraction: In English, are retracted before . Because the choice among allophones is seldom under conscious control, few people realize their existence. English-speakers may be unaware of differences between a number of (dialect-dependent) allophones of the phoneme : post-aspirated as in top, unaspirated as in stop. glottalized (or rather