Make sure you're back by midnight.
Synonyms and examplesbeforeTry to arrive before the start of the meeting.
prior toAll utensils should be washed prior to use.
in advance offormalCall in advance of your visit to see if you'll need a parking reservation.
ahead ofMy sister is arriving ahead of me to do the shopping for the dinner.
Antonym and exampleafterShe showed up after the meeting had started.
Go to the thesaurus article about these synonyms and antonyms ofby.
See alsobeforehand
previously
in advance
ahead of timemainlyUS
ahead
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The prepositionbeforeshows that one event happens earlier than another. Before is also ad adverb meaningat an earlier time.