o'clock
- 1Used with a number from one to twelve to state the moment when the hour hand points exactly at that number, marking the top of the hour.
The meeting was scheduled for ten o'clock, but half the team arrived early.
By four o'clock the light had already begun to fade across the valley.
Note
Behind the apostrophe is a whole phrase: of the clock, Middle English of the clokke, in use since the late 14th century. It pairs only with whole hours, so it is two o'clock but never two-fifteen o'clock. The phrase could also stand on its own. In Sir Arthur Conan Doyle's The Adventures of Sherlock Holmes (1892), Holmes asks, "what o'clock is it?", treating o'clock almost as a noun.
- 2Used with a number to indicate direction relative to oneself or a vehicle, with twelve meaning directly ahead (or straight up) and three meaning to the right.
The pilot reported another aircraft at his two o'clock, slightly below his altitude.
The lookout called out a ship approaching from eleven o'clock off the bow.
Note
The clock face becomes a dial of directions, laid flat around the observer or stood upright before the eyes. Pilots are only one group of users. Bird watchers use it to point out a hard-to-spot perched bird, and lab instructors use it to steer students around a microscope's field of view. Aileen R. Lotz's Birding around the year (1989) warns that you need to know your "o'clocks" (nondigital), because the system assumes a dial with hands.
- 3Used to indicate that the time has arrived to do a specific thing, or for a specific thing to happen.
She kicked off her shoes and announced that it was officially couch o'clock.
Once the kids are asleep, it's wine o'clock for the exhausted parents.
Note
Here a noun takes the numeral's place: beer o'clock, waffles o'clock, dinner o'clock. The clock announces an activity instead of an hour. The joke is older than it sounds. Henrietta A. Duff's Honor Carmichael (1880) already describes English households keeping "a daily calendar of feasts — breakfast o'clock, dinner o'clock." The tone is humorous and informal, so it belongs in conversation and casual writing, not in formal prose.
Practice
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Origin
A shortened form of "of the clock," from Middle English "of the clokke," dating from the late 14th century.