abril. Note it is not normally capitalized, except at the beginning of a sentence.
Abril.
El primero de abril
You can say "No Abra hasta el 4 de abril". Note that the names of the months are not capitalized in Spanish.
You can say, "Mi cumpleaños es el 11 de abril" in Spanish. This translates directly to "My birthday is on the 11th of April."
"20 de abril"
The month "April" is abril in Spanish.
Vacaciones de Semana Santa Vacaciones de abril
The month of April in Spanish is abril.
The abbreviation for April in Spanish is "abr."
veinte y tres de abril 2008
su cumpleaños es el 1 de abril
El veintitrés de abril de mil seiscientos dieciséis.