Religious Women

Woman who has professed vows in a religious order: Sister [First Name]

Superior of a community: Mother [First Name] (or Reverend Mother)

As a note: There are exceptions to these rules, as some religious orders have differing titles and appointments.

Religious Men

Man who has professed vows in a religious order: Brother [First Name] (or Reverend Brother)

Superior of a community, usually a priest: Father [First Name], or Abbot [First Name] (or Your Excellency)

As a note: There are exceptions to these rules, as some religious orders have differing titles and appointments.

Deacon

Deacon [First Name or Last Name]

Reverend Mister [First Name] is a more formal salutation.

Deacons in the Eastern Rite Churches are usually addressed as Father Deacon.

Priest

Father [First Name] (In the United States it is often customary to address a priest by his Last Name)

Reverend Father can be used on more formal occasions.

Note that Reverend by itself is never used as a title of direct address in the Catholic Church. It is an adjective, but may be shortened to Rev. in place of Fr. in a written address.

Monsignor

Monsignor [First Name] 

Reverend Monsignor or Your Reverence can be used on more formal occasions.

Bishop

Bishop (or Archbishop) [Last Name] is customary in the United States.

Most Reverend [First and Last Name] or Your Excellency on more formal occasions.

Patriarch

This is in regards to members of the Eastern Catholic hierarchy.

Your Beatitude [First and Last Name]

Cardinal

Cardinal [Last Name] is customary for informal situations in the United States.

When addressing an envelope, the formula is [First Name] Cardinal [Last Name].

Your Eminence or My Lord Cardinal is used on more formal occasions.

Pope

Pope [Name] is the informal way to address the pope.

Your Holiness or Holy Father is the formal way to address the pope.