Tense vowels:
* Muscular effort: Produced with a higher degree of muscle tension in the tongue and jaw.
* Duration: Generally longer in duration than lax vowels.
* Quality: Often have a more "pure" or "clear" sound, with a more defined vowel quality.
* Examples in English: /i/ (as in "see"), /e/ (as in "say"), /u/ (as in "too"), /o/ (as in "go")
Lax vowels:
* Muscular effort: Produced with less muscle tension in the tongue and jaw.
* Duration: Generally shorter in duration than tense vowels.
* Quality: Often have a more "diphthongized" or "reduced" sound, with less defined vowel quality.
* Examples in English: /ɪ/ (as in "sit"), /ɛ/ (as in "set"), /ʊ/ (as in "put"), /ɔ/ (as in "caught")
Key differences in English:
* Tense vowels are typically found in stressed syllables, while lax vowels are often found in unstressed syllables. For example, the word "about" has a tense vowel in the stressed syllable "a" (/əˈbaʊt/) and a lax vowel in the unstressed syllable "bout" (/əˈbaʊt/).
* Tense vowels can appear in both long and short words, while lax vowels are generally found only in short words. For example, "beat" (with the tense vowel /iː/) is a short word, but "believe" (with the tense vowel /iː/) is a longer word.
* Tense vowels often precede voiceless consonants, while lax vowels often precede voiced consonants. For example, "feel" (tense vowel /iː/) ends in a voiceless consonant, while "fill" (lax vowel /ɪ/) ends in a voiced consonant.
Note:
* The distinction between tense and lax vowels can be subtle and may vary depending on the dialect of English.
* There are exceptions to these general rules.
* It's important to remember that these are phonetic descriptions of the sounds. They don't necessarily reflect the spelling of the words.
For a deeper understanding, consult a phonetics textbook or a reliable online resource.