If you mean the side arms of a church, it is called "the transept". Each of the two may contain a chapel.
Christ Church Chapel was created in 1923.
A chapel is like a church.
Johnson's Chapel AME Church was created in 1872.
Christ Church Royal Chapel was created in 1784.
Joshua Chapel A.M.E. Church was created in 1917.
Freeman Chapel C.M.E. Church was created in 1923.
Chapel Hill Bible Church was created in 1973.
Highland Chapel Union Church was created in 1906.
Williams Chapel A.M.E. Church was created in 1915.
Washington Chapel C.M.E. Church was created in 1907.
Reedy Chapel-AME Church was created in 1886.