"by", a common English preposition;
by or bye, a free pass through a round of competition in a tournament;
Bavaria (BY), official abbreviation of the German federal state Bavaria;
By, Doubs, a commune in the Doubs département of France;
Belarus (BY), WMO and 2-letter ISO country code
.by, the ccTLD for Belarus;
;
Britannia Airways IATA airline code;
Burundi (BY), FIPS Pub 10-4 and obsolete NATO digram country code;
By, John Lieutenant-Colonel, 19th century British military engineer famous for his work in Canada;
Byelorussian Soviet Socialist Republic, obsolete (1992) 2-letter ISO country code;
Thomsonfly IATA airline code;