Let's try to understand the use of /i/. Here you can read John Wells's explanation

Thursday, 29 April 2010
re-
Dear Professsor Wells,
I’m confused about the pronunciation of the prefix re-. When does it have the DRESS vowel? LPD says “if stressed through the operation of a stressing rule”, but I don’t understand what that means.
XYZ

Let’s try to set out the facts about this prefix using a different approach.

1. When re- means ‘again’, it is pronounced ri: and stressed. So we have for example reapply, renegotiate, reconsider, all with ˌriː-. In words such as refit, rethink, rerun we get the familiar stress difference between verb and noun, but the first part is always riː. A ˈrefit, but to ˌreˈfit. So far, the rule is easy.

2. When re- has a vaguer meaning, it usually gets weakened and is unstressed. We have ri- or rə- (it doesn’t matter which) in words like remember, retain, remarkable, repeat. This rule is easy, too. However, if the sound immediately after the re- is a vowel, then we always have ri- (= riː- or rɪ or something intermediate). The only important example is react riˈækt and its derivatives.

3. Now we come to the tricky bit. If re- has the vague meaning AND IS STRESSED, AND IS FOLLOWED BY A CONSONANT SOUND, then it is pronounced re-. This type includes several well-known words: relative ˈrelətɪv, recognize, reference, relevance, and also for example recompense, replicate, resonate. (Compare relate, refer, where the re- is unstressed and weak.)

4. If the main stress is on the syllable after the syllable after the re- (= two syllables later), we normally get secondary stress on the re-, which therefore has a strong vowel, which again is e. So we have for example reclamation ˌrekləˈmeɪʃən (compare the verb reclaim with weak re-), recognition, recommend ˌrekəˈmend, recreation, reformation, relativity, reparation, repetition, replication, reprehensible, represent, reservation, resignation, restoration.
Types 3 and 4 are therefore the words I mean when I say “if stressed…”. They are the ones that present the greatest problem for learners of EFL.

5. This being English, some words are irregular and exceptional. For example, many people pronounce one or all of relaxation, resistivity, retardation in a way that violates the above rules.

6. These principles also apply to de- and pre-. Examples: 1. deconstruct, predetermine; preprint; 2. decide, prepare; 3. deference, preference; 4. dereliction, preparation; 5. AmE treats premature as having the explicit meaning ‘before’ (ˌpriː-); BrE treats it as having the vague meaning (ˌpre-).

Sorry, it’s still pretty complicated.
Posted by John Wells at 10:24 8 comments