What Is O A - Public Sports

MSN: What is O-1 visa? Here's why ‘genius visa’ getting popular amid H-1B woes What is O-1 visa? Here's why ‘genius visa’ getting popular amid H-1B woes What is the difference between O & O2 - Chemistry Stack Exchange As pointed out by @Charo below, accent marks are always used to denote stress, but with "e" and "o" they also tell you how to pronounce the vowel.

So, how can I decide whether to write plain o, when to write ò, and when to write ó, and what is the exact difference between these? Thanks.