A helpful resource for hearing how English speakers pronounce things is Youglish. You can listen to [its examples for *enum*][1] to confirm that, as tchrist says, the first syllable is generally pronounced as /i/ (the same as the name of the letter E).

However, even if it is only used by a few speakers, it seems a pronunciation with an unstressed first syllable with a reduced vowel also exists (either /əˈnum/ or /ɪˈnum/), as demonstrated by the following links:

- [Crockford on JavaScript - Level 7: ECMAScript 5: The New Parts](https://www.youtube.com/watch?v=UTEqr0IlFKY&t=1562s) (Douglas Crockford, at 26:03)

- [Navigation: SafeArgs - MAD Skills](https://www.youtube.com/watch?v=8I8Xykqn4hk&t=456s) (Chet Haase, at 7:40)

- [Jeffrey Richter Using Reflection to implement enumerated types](https://www.youtube.com/watch?v=DyXJy_0v0_U&t=933s) (Jeffrey Richter, at 15:33 and again at 15:54)

While you did not want information about the second syllable, others may be interested to know that it can either be /num/ or /nʌm/ (or /nəm/).

I don't think "Which one is correct?" is a very meaningful question, but in any case, if you use the pronunciation recommended by tchrist, you shouldn't have to worry about it.


  [1]: https://youglish.com/pronounce/enum/english/all/cptc=1