Free variation

Free variation in linguistics is the phenomenon of two (or more) sounds or forms appearing in the same environment without a change in meaning and without being considered incorrect by native speakers. Examples from English include:
 * glottalization of voiceless stops in word-final position: for example, the word stop may be pronounced with a plain unaspirated, , or with a glottalized ,
 * the word economics may be pronounced with or  in the first syllable; although individual speakers may prefer one or the other, and although one may be more common in some dialects than others, both forms are encountered within a single dialect and sometimes even within a single idiolect
 * the comparative of many disyllabic adjectives can be formed either with the word more or with the suffix -er, for example more stupid or stupider.

When phonemes are in free variation, speakers are strongly aware of the fact, and will note, for example, that tomato is pronounced differently in British and American English, or that either has two pronunciations which are fairly randomly distributed. However only a very small proportion of English words show such variations. In the case of allophones, however, free variation is exceedingly common and along with differing intonation patterns is the most important single feature in the characterising of regional accents.