Apostrophe Word Clock Takes Place O'clock Phrase On 

An apostrophe is used in o'clock because the word is a contraction of the phrase "of the clock." Just like other contractions, the apostrophe takes the place of missing words or letters from a longer word or phrase. For example, the apostrophe in "don't" takes the place of 'o' in the word "not," and the apostrophe in "you'll" takes the place of 'wi' in the word "will."

When we use the word o'clock we are saying that it is a particular hour "according to the clock." For example, "it is almost four o'clock" means the same as "it is almost four according to the clock." However, the full phrase "of the clock" is not used by native English speakers. Always use the shortened form, "o'clock."

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