Petroleum (Latin Petroleum f. Greek πέτρα (Latin petra) - rock + έλαιον (Latin oleum) - oil) or crude oil is a naturally occurring liquid found in formations in the Earth consisting of a complex mixture of hydrocarbons (mostly alkanes) of...

Petra Strorm, in John Wyndham's novel The Chrysalids.

Petra (band), a Christian rock band

Petra usually refers to the archeological site in Jordan. Other meanings of the word:

Petra Kelly, a German peace activist

Petra Verkaik, a model known for her many appearances in Playboy

Petra Marklund, a Swedish singer, pseudo "September"

Petra Nemcova, a Czech supermodel

Petra Arkanian, a fictional character in a book series by Orson Scott Card

Petra Haden, a singer and violinist

Petra (comics), a Marvel Comics character

Peter (name)

Petra, Lesbos

Petra (album), the debut album of the band mentioned above.

Petra, Spain, a town on the island of Majorca

Petra Frey, an Austrian singer

Petra (agency), the Jordanian news agency

Petra Vaideanu, a Romanian heptathlete

Petra de Steur, a Belgian singer also known as La Sakhra

Petra, Pieria

Petra Andalee, the protagonist that appears in Blue Balliett's Chasing Vermeer and The Wright 3

Petra (dog), a dog on the children program Blue Peter

Petra, a female meerkat shown in Meerkat Manor

Petria (brachiopod), a brachiopod genus.

Petria Thomas, Australian swimmer.