Free variation refers to a phenomenon whereby a word can be pronounced in two different ways which are acceptable to native speakers. The word free is not entirely accurate, however, because for most speakers one form is preferred over another. English has many examples of free variation.
Words with two different pronunciations include either, neither, data, status, bouquet, Caribbean, economic, divisive, often and kilometre.
The words either and neither can be pronounced with the vowel of me or the vowel of my. I use the vowel of me.
The words data and status can be pronounced with the vowel of mat or mate. I use the vowel of mate in data and the vowel of mat in status.
The word bouquet can be pronounced with the vowel of toe or two. I use the vowel of two.
The word Caribbean can be stressed on the second syllable or on the third. I stress it on the third.
The word economic can be pronounced with the vowel of met or meet in the first syllable. I use the vowel of met.
The word divisive can be pronounced with the vowel of sit or site in the first syllable. I use the vowel of site.
The word often can be pronounced with or without a t. I pronounce it without a t. A word with a silent t (no free variation) is listen.
The word kilometre can be pronounced so that it rhymes with thermometer or with the same pronunciation as in the word metre. I pronounce kilometre with the pronunciation of metre.
English is a language with many examples of free variation. This is in contrast to many other languages in which free variation is not so common. However, it is important to note that the two different pronunciations of a word usually do not vary so freely because most speakers prefer one pronunciation over another.