The big O
No, not that big O.
O and oh were once no more than variant spellings, but a differentiation in meaning has developed.
O—you can call it the vocative O if you like Latin terms of grammar—is the form used in direct address to a person, a deity, an audience. “O say, can you see. ...” Reserve it for such direct address.
Oh can be a mere interjection, as in “Oh, I forgot to mention. ...” But it is more often an exclamation, indicating surprise, dismay, disgust, excitement, joy, or some other emotion. That is the oh abbreviated in the adolescent text abbreviation OMG. There is speculation that it is often a person’s next to last word.
Comments
Mathematicians and computer scientists talk of "big-O" (or "big-oh") notation for representing approximately how fast something grows when you add new inputs to it. Linear growth is O(n), quadratic growth is O(n^2), and exponential growth is O(2^n). There is also little-O notation, but it is much less used.
Posted by: John Cowan | August 6, 2010 3:52 PM
Then there is the poetic or dramatic "O," which I like.
Posted by: Patricia the Terse | August 6, 2010 6:14 PM
Then, of course, there is the "O" used to identify Oprah Winfrey's magazine. It has become so popular that people don't bother to explain the reference any more. They just say, "I read in O that...."
Posted by: Jed | August 7, 2010 6:04 AM