How to pronounce the letter 'i'
I'll elaborate a bit on Barrie's point, which is correct, if disappointing.
The problem is that English spelling was not designed for Modern English. It was designed for Middle English, a very different language. When Middle English changed its pronunciation to become Modern English, English spelling did not change. Furthermore, English borrowed many thousands of words from other languages, which were of course pronounced differently, and spelled differently still.
The result is that one has to choose between two strategies in learning English words, however they are spelled -- this is not a problem confined to the letter I -- or else figure out some way to mix them.
Either you can actually learn the historical rules about pronunciation and learn to distinguish the different kinds of word each rule applies to -- which amounts to learning some basic linguistics,
Or you can do as Barrie suggested, and memorize 2 things about every word you learn -- (1) how it's spelled and (2) how it's pronounced (Kenyon and Knott is your friend here) -- and just ignore the possible but treacherous correspondences you might suspect between Middle English or foreign spellings and Modern English pronunciations.
The second option amounts to giving up all hope of making sense of English spelling. Most native English speakers do this, which is simpler for them, since they already know the pronunciation.
Since Anglophone education systems don't teach anything about English language, they never learn any different, and many still believe there should be a simple rule for pronouncing every letter.
i is pronounce as /aɪ/ when i + consonant + e as in: time, site, fire, to entire, ...
This is a special case of the "magic e" rule: vowel + consonant + e = "long" vowel. It's a fine rule that accurately describes pronunciation — most of the time.
Some silent e's do not lengthen the vowel, but serve other purposes:
- To prevent a word from ending in "v", as in "give" and "live".
- To "soften" a "c", as in "notice", "office", and "practice".
OTOH, some words ending in "ce" or "ve" do have a long vowel ("ice", "hive").
I can't determine why "engine" and "opposite" have short i's.
i is pronounce as /aɪ/ when i is followed by gh as in: sigh, sight, thigh, ...
"Eigh" is pronounced /eɪ/. (Eight reindeer pull the weight of Santa's sleigh.) Otherwise, I can't think of exceptions to this rule.
i is pronounce as /aɪ/ when i is preceded by a as in: aisle, ...
I'm afraid that I must raise an objection here. The main pronunciation of "ai" is /eɪ/. (The rain in Spain falls mainly on the plain.)
Again, all English spelling rules are certain to have exceptions, like the /ɪ/ in "mountain".
The word "said" seems to be unique in prouncing "ai" as /ɛ/.
Some more rules you could use are:
- "tion" is pronounced /ʃən/
- "ing" is prounounced /iŋ/ (or informally, /ɪn/)
- "oi" is pronounced /ɔɪ/
- "i" followed by a double consonant (or "ck", "dg", "tch") is pronounced /ɪ/.
So, I know (or I believe to know), that it is hard to make pronunciation rules for English words. But how can I improve my gut feeling, pronouncing new words correctly?
Start by learning the pronunciation first, and then learn the spelling. You'll know that a word is spelled right when the wavy red line under it disappears. That's what native speakers do.
As John says, there are a lot of things to consider when trying to figure out a specific word's pronunciation. I will point out, though, that I think your rules 3 and 4 are wrong, and you could supplement them with a few other rules.
3: ai is (almost) always pronounced /eɪ/: fail, pail, mail, curtail... (aisle is an exception to this common rule.)
4: a y is not an i, it has its own rules. :-)
5: ity at the end of a word is pronounced /ɪti/: gravity, city, pity...
6: ie at the end of a word is (mostly) pronounced /aɪ/: pie, lie, die..., but is /i/ if it is unstressed, as a nickname or a diminutive: Sissie, Bettie, budgie.
7: ier at the end of a word depends on the pronunciation of the word without the er: messy (mess-i) -> messier (mess-i-r), but deny (di-naɪ) -> denier (di-naɪ-r). (But pier and tier, not being stem + -er forms, are pronounced with an /ɪəʳ/.)