O

Oak Allée The correct spelling
   
OK OK (without periods) or okay are preferred uses.
   
older adults A New York Times poll found that this population dislikes being identified as the elderly, preferring identification as older adults or seniors.
   
Olin Business School

Use the full name, Olin Business School at Washington University in St. Louis, on first reference. Olin is acceptable in later references.

For business school publications, use the graphic look created for Olin.

   
ongoing  
   
online  
   
over

Generally, use more than for amounts and over for spatial relationships.

However, it is all right to use over in the context of having exceeded a goal: “The campaign for the YMCA raised over $17.9 million.”

Over in the sense of more than is becoming increasingly used in less formal language.