The following example illustrates different cases:
Within that charmed rock, so Torridge boatmen tell, sleeps now the old Norse Viking in his leaden coffin, with all his fairy treasure and his crown of gold; and, as the boy looks at the spot, he fancies, and almost hopes, that the day may come when he shall have to do his duty against the invader as boldly as the men of Devon did then. And past him, far below, upon the soft south-eastern breeze, the stately ships go sliding out to sea.
OR.—The rules for the conjunction "and" apply with little change to the conjunction "or"; but there are one or two special points to note.
(a) When "or" is preceded at no great distance by "either" or "whether," the two words should be separated by no point.
They must either yield this point or resign.
It does not matter whether we go or stay.
But a point is inserted if the words stand farther apart, or if each is followed by a complete clause.
Either this road leads to the town, or we have misunderstood the directions.
(b) "Or," joining two alternatives, takes no point before it; but when it joins two words that are used, not as real alternatives, but as synonyms, a comma is inserted.
England or France might be asked to join the alliance.