By or BY may refer to:
The Byzantine Empire, also referred to as the Eastern Roman Empire and Byzantium, was the continuation of the Roman Empire in its eastern provinces during Late Antiquity and the Middle Ages, when its capital city was Constantinople (modern-day Istanbul, which had been founded as Byzantium).
The bystander effect, or bystander apathy, is a social psychological phenomenon in which individuals are less likely to offer help to a victim when other people are present.
The BYU Cougars football team is the college football program representing Brigham Young University (BYU), a private university owned by the Church of Jesus Christ of Latter-day Saints and located in Provo, Utah.
The Byelorussian Soviet Socialist Republic (BSSR, or Byelorussian SSR; Belarusian: Беларуская Савецкая Сацыялістычная Рэспубліка, translit.
The Byzantine Rite, also known as the Greek Rite or Constantinopolitan Rite, is the liturgical rite used by the Eastern Orthodox Church, as well as by certain Eastern Catholic Churches and Byzantine Rite Lutheranism, which have adapted it to their respective tradition.
The Byzantine–Sasanian War of 602–628 was the final and most devastating of the series of wars fought between the Byzantine (Eastern Roman) Empire and the Sasanian Empire of Iran.
Bydgoszcz (Polish: [ˈbɨdɡɔʂt͡ʂ] ( listen); German: Bromberg [ˈbʁɔmbɛɐ̯k]; Latin: Bydgostia) is a city in northern Poland, on the Brda and Vistula rivers.