In weakly stressed positions, vowels may become voiceless between two voiceless consonants: ('exhibition'), ('because'). This may also happen in cases where only the following consonant is voiceless: ('skull'). Because of mergers of different phonemes in unstressed position, the assignment of a particular phone to a phoneme requires phonological analysis. There have been different approaches to this problem:   Russian diphthongs all end in a non-syllabic , an allophone of and the only semivowel in Russian. In all contexts other than after a vowel, is considered an approximant consonant. Phonological descriptions of may also classify it as a consonant even in the coda. In such descriptions, Russian has no diphthongs. The first part of diphthongs are subject to the same allophony as their constituent vowels. Examples of words with diphthongs: ('egg'), ('her' dat.), ('effective'). , written or , is a common inflexional affix of adjectives, participles, and nouns, where it is often unstressed; at normal conversational speed, such unstressed endings may be monophthongized to .   denotes palatalization, meaning the center of the tongue is raised during and after the articulation of the consonant. Phonemes that have at different times been disputed are enclosed in parentheses. There is some dispute over the phonemicity of soft velar consonants. Typically, the soft–hard distinction is allophonic for velar consonants: they become soft before front vowels, as in ('short'), unless there is a word boundary, in which case they are hard (e.g. 'to Ivan'). Hard variants occur everywhere else. Exceptions are represented mostly by:  The rare native examples are fairly new, as most them were coined in the last century:  In the mid-twentieth century, a small number of reductionist approaches made by structuralists put forth that palatalized consonants occur as the result of a phonological processes involving (or palatalization as a phoneme in itself), so that there were no underlying palatalized consonants. Despite such proposals, linguists have long agreed that the underlying structure of Russian is closer to that of its acoustic properties, namely that soft consonants are separate phonemes in their own right. Voiced consonants (, and ) are devoiced word-finally unless the next word begins with a voiced obstruent. also represents voiceless word-finally in some words, such as .