Sorry for this delayed reply. I missed reading your posting and it’s only now that I came across it in the ‘Use and Misuse” discussion board.
Normally, the conjunction “or” is used to indicate an alternative or distinguish between two choices, as in “You can take the morning flight
or the one in the evening?” and “Do you prefer coffee
or tea?” In the case of one-word alternatives or those that consist of a phrase of just a few words, there’s no need for a comma to precede the “or.” When the alternative or choices are in the form of rather long phrases, however, using a comma before the “or” may become advisable for clarity’s sake, as in “It’s possible that the newly married couple will consider buying a condominium unit when they move to the city proper next month
, or they might just rent an apartment if they can find one near enough to the university where they’ll both be teaching.” Now imagine that long sentence without the comma before “or” and read it.
RELATED READINGS:“On the question over my use of the serial comma”“Why I consistently use the serial comma”
