O

okay

Note spelling; this is academic style rather than journalistic.

online

> See: computer terms

on-site (adj.), (adv.)

on vs. upon

Upon is a stuffy, overly formal way of saying on. The exception is when upon is used to make a time reference.

We decided on a new restaurant for lunch.
BUT Credits will be transferred upon graduation.

oral, verbal

Use oral to refer to spoken words:

She gave an oral promise.

Use verbal to compare words with some other form of communication:

His tears revealed the sentiments his poor verbal skills could not express.

over

> See: more than vs. over