Finite is pronounced ['faɪnaɪt] while infinite is pronounced [ˈɪnfɪnɪt]. So why is the vowel in the first syllable of 'finite' different from the vowel in the second syllable of 'infinite'?
OK, it's not because of Trisyllabic Laxing, I made an erroneous assumption which I deeply regret.
The answer is actually simple. As Luigi Burzio explains in Principles of English stress, the reason boils down to English stress patterns.
The diphthong [aɪ] (as in bite) almost never occurs in unstressed syllable. The diphthong [aɪ] has a systematic relationship with the short vowel [ɪ]. This relationship is also reflected in Trisyllabic Laxing; divine-divinity, derive-derivative and in drive-driven etc.
From this relationship, we can infer a general rule of thumb that [aɪ] will only occur in stressed syllables and when that syllable gets unstressed, [aɪ] will shorten to [ɪ].
Now when you prepend the prefix in- to finite, the primary stress moves to the prefix in- because it's a stress-bearing affix.
- In + f[aɪ]nite → inf[ɪ]nite
- In + p[əʊ]tent → imp[ə]tent
- In + m[aɪ]grant → imm[ɪ]grant
- In + f[eɪ]mous → inf[ə]mous
Another example would be cycle-bicycle:
- Bi + c[aɪ]cle → bic[ɪ]cle
There are exceptions, however. Luigi Burzio has explained all the rules and exceptions thoroughly in his book. One of the many exceptions is the prefix un- which doesn't take primary stress, for instance, unab[eɪ]ted.
Latinate words in English tend to be stressed on the penultimate (second last) syllable unless that syllable is short, in which case the primary stress falls on the antepenult (third last syllable) but not on preantepenult (fourth last) as far as I know. That's why impossible, implausible, incredible etc., are stressed on the antepenult.
The only examples I can find after searching are proper nouns: The city of Quincy (/ˈkwɪnzi/ KWIN-zee) as mentioned in comments, and the highest mountain in Australia Mount Kosciuszko (/ˌkɒziˈʌskoʊ/).
Standard (i.e. RP or GA) pronunciations of sacrifice and discern now use /s/.
Best Answer
𝑇𝐿;𝐷𝑅
'Lose' came from Old English (OE) word losian while 'loose' was taken from Old Norse around the thirteenth century. There was a process in OE through which s, f and th became voiced respectively to [z], [v] and [ð] when they occurred between voiced sounds i.e. between two vowels or a vowel and anther voiced sound. There was no phonemic contrast of voice among the OE fricatives.
The ⟨s⟩1 in the OE form of 'lose' was intervocalic (between vowels), so it became [z] which survived into Modern English (ModE).
'Loose' came into English in the thirteenth century by the time the voicing was no longer productive, so it retained the original [s] sound.
𝐸𝑥𝑝𝑙𝑎𝑛𝑎𝑡𝑖𝑜𝑛
There are lots of pairs that exhibit the same sound change such as wolf/wolves, bath/bathe, house (n)/house (v), breath/breathe, life/lives, loaf/loaves, close (adj)/close (v), knife/knives, cloth/clothes etc. All these are the remnants of OE property called intervocalic fricative voicing
Fricative voicing
Old English had a phonetic property called fricative voicing, whereby non-velar fricatives—s, þ ~ ð2, f—became voiced when they were flanked by vowels, or a vowel and another voiced consonant. The fricatives s, þ ~ ð, f were voiceless elsewhere. /ʃ/ was always voiced.
There were no distinctive voiced fricatives in Old English. The realisations [f - v], [θ - ð] and [s - z]3 were allophonic. It was the only way to get [z], [v] and [ð] because Old English didn't have phonemic [z], [v] and [ð]. In a nutshell:
Examples
Note that the fricatives were phonemically voiceless; the voicing was allophonic.
Lose vs loose
Lose came from Old English losian. The s was intervocalic, so it became [z] due to that property:
In Middle English, it became losen ([ˈloːzən]), then it lost the terminal nasal and became [ˈloːzə], then the terminal schwa was lost and the vowel [oː] was changed to [uː] by the Great Vowel Shift.
Loose entered English in the 13th century and by that time, the voicing wasn't productive anymore. So it retained its original /s/.
𝐍𝐎𝐓𝐄𝐒