Contra is a preposition with obvious connections to the English prefix "contra-," usually indicating some sort of opposition or contrast. In most cases it is the rough equivalent of the English preposition "against."

Perhaps the most common use of contra is to mean "against" with the meaning of "in opposition to":

• La Unión Europea decidió imponer sanciones contra el presidente. (The European Union decided to impose sanctions against the president.)

• Se dedican a la lucha contra la explotación. (They are dedicated to the fight against exploitation.)
• Fue aprobada una medicina contra el cáncer en los EE.UU. (A medicine against cancer was approved in the U.S. An anti-cancer medicine was approved in the U.S.)
• ¡No más violencia contra las mujeres! (No more violence against women!)
• La opinión pública está contra la construcción de plantas nucleares. (Public opinion is against the construction of nuclear plants.)
• Todos están contra mí. (Everybody's against me.)

Contra can also mean "against" when referring to location. Other translations of the preposition are often used:

• La silla está contra la pared. (The chair is against the wall. The chair is next to the wall.)
• El biciclista chocó contra el árbol. (The bicyclist crashed against the tree. The bicyclist crashed into the tree.)
• La tiró contra la casa. (He threw it against the house. He threw it at the house.)

It is common to substitute the phrase en contra de for contra when it means "in opposition to":

• Tengo cinco objeciones en contra de la ley. (I have five objections against the law.)
• Sobrevivió en contra de la adversidad. (She survived against the adversity.)
• Los trabajadores están en contra de nuevos horarios. (The workers are against the new schedules.)

The phrase en contra de que is used similarly before a verb:

• Su madre estaba en contra de que fuera cantante. (Her mother was against her being a singer.)
• Los profesores no están en contra de que el líder estadounidense venga al país. (The teachers are not against the U.S. leader coming to the country.)
• El 61% están en contra de que el presidente vete la ley. (Sixty-one percent are against the president vetoing the law.)