I am not a native English speaker and thus the variation of pronunciation always amazes me. How can the exact prefix or letters pronounced so differently in some words, for example:
Accent is pronounced as "æksənt" and Acceleration as "əkˌseləˈreɪʃn" - almost as if it is written with an "i" as (icceleration).
Enter as "entər" and Entangle as "Inˈtæŋɡl" - again as if written with an "i" .
Trivial as "trɪviəl" and tribunal as "traɪˈbjuːnl"
These are only few examples as there are many other prefixes with this type of variations in pronunciation. Why is this, What am I missing and is there a rule of thumb for pronouncing these kind of prefixes?
Every answer and opinion will be greatly appreciated.