“O Mary, go and call the cattle home.”
“O God, whose thunder shakes the skies.”
“Oh! say, can you see by the dawn’s early light”—
“Oh! why should the spirit of mortal be proud?”
open up is properly used to signify “explore; discover; as, to open up a new country,” but not so in the sense of “introduce; as, to open up a subject.” Here the word up is superfluous; but in this, as in the majority of cases where open up is used, it would be better to substitute a more specific term. See [UP].
opinion is sometimes more than an impression, being a conclusion or judgment held with confidence, though falling short of positive knowledge. The word should therefore not be used interchangeably with idea, which may be a mere conception, with or without foundation for its belief. One may have an idea of enjoyment, but hold an opinion on the result of a campaign.
oral should be differentiated from verbal. The former applies to what is spoken by mouth, whereas the latter indicates that which has been reduced to words.
orate: A term to avoid when “speak, declaim, harangue,” or a like word will express what is intended. It may, however, be fittingly used meaning “to play the orator, talk windily in round periods”: it meets the canon of “supplying an antecedent blank,” and is a legitimate word, especially in humorous or contemptuous use.
ordinance, ordnance: These words have no relation in common. An ordinance is a regulation ordained by some one in authority as a “municipal ordinance.” Ordnance is artillery, especially heavy guns, cannon of all kinds, mortars, howitzers, etc.