These are probably confused with each other more often through haste than through actual ignorance, but “by” is the common preposition in phrases like “you should know by now.” It can also serve a number of other functions, but the main point here is not to confuse “by” with the other two spellings: “’bye” is an abbreviated form of “goodbye” (preferably with an apostrophe before it to indicate the missing syllable), and “buy” is the verb meaning “purchase.” “Buy” can also be a noun, as in “that was a great buy.” The term for the position of a competitor who advances to the next level of a tournament without playing is a “bye.” All others are “by.”
This is the ten-year anniversary of the Common Errors in English Usage calendar. To celebrate, we are bringing back some of our favorite interesting, funny, but sometimes merely silly entries through the years before going on hiatus in 2016.
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