In phonetics and phonology, checked vowels are those that commonly stand in a stressed closed syllable; and free vowels are those that can stand in either a stressed closed syllable or a stressed open syllable.
The terms checked vowel and free vowel originated in English phonetics and phonology. They are seldom used for the description of other languages even though a distinction between vowels that usually have to be followed by a consonant and other vowels is common in most Germanic languages.
The terms checked vowel and free vowel correspond closely to the terms lax vowel and tense vowel respectively, but many linguists[who?] prefer to use the terms checked and free, as there is no clearcut phonetic definition of vowel tenseness and because by most attempted definitions of tenseness and are considered lax even though they behave in American English as free vowels.
Checked vowels is also used to refer to a kind of very short glottalized vowels found in some[which?]Zapotecan languages that contrast with laryngealized vowels. The term checked vowel is also used to refer to a short vowel followed by a glottal stop in Mixe, which has a distinction between two kinds of glottalized syllable nuclei: checked ones, with the glottal stop after a short vowel, and nuclei with rearticulated vowels, a long vowel with a glottal stop in the middle.
In English, the checked vowels are the following:
There are a few exceptions, mostly in interjections: eh with ; duh, huh, uh, uh-uh, and uh-huh with ; nah and yeah with . There are also the onomatopoeia baa for and the loanword pho for when pronounced in American English. The proper names Graham and Flaherty are sometimes pronounced with a prevocalic .
The free vowels are the following:
The term checked vowel is also useful in the description of English spelling. As free written vowels a, e, i, o, u correspond to the spoken vowels , , , , ; as checked vowels a, e, i, o, u correspond to , , , , . In spelling free and checked vowels are often called long and short, based on their historical pronunciation, though nowadays some or all of the free vowels are diphthongs, depending on the dialect, not long vowels as such. Written consonant doubling often shows the vowel is checked; the i of dinner corresponds to checked because of the double consonants nn; the i of diner corresponds to free because of the single consonant n. This, however, interferes with the differences in doubling rules between American and British styles of spelling, say travelled versus traveled. Similarly, a "silent e" following a single consonant at the end of a word often indicates that the preceding vowel is free where it would otherwise be checked; for example, the a of tap corresponding to whereas that in tape corresponds to .