讀英語研究所的時候，有位華人教授大約中學時移民美國，在美國讀到語言學博士。她說
英語極為流利，只聽聲音會誤會是洋人。有次上課她把an NBA player說成a NBA player
。被碩士生指出來，她竟然說2種說法都可以。The correct form is:
**an NBA player**
This is because **a/an** depends on the **sound**, not the spelling.
* **NBA** is pronounced **"en-bee-ay"** /ш.bieɪ/.
* It begins with the vowel sound **/ɛ/** ("en").
Therefore:
* **an NBA player** * **a NBA player**
Similar examples:
* **an NBA game**
* **an NFL coach** (NFL = "en-eff-el")
* **an FBI agent** (FBI = "eff-bee-eye")
* **an MBA student** (MBA = "em-bee-ay")
But:
* **a NATO official** (NATO is pronounced "NAY-toe," starting with a
consonant sound /n/)
* **a UNESCO program** (UNESCO is often pronounced "you-NESS-co," starting
with /j/)
A useful rule:
> Use **an** before a vowel **sound**; use **a** before a consonant **sound**.
So we say:
> **Michael Jordan was an NBA player.**
not
> **Michael Jordan was a NBA player.**
(And if you say the full phrase **National Basketball Association player**,
it becomes **a National Basketball Association player**, because "National"
begins with the consonant sound /n/.)