Simplify the following text for a Grade 11 native English-speaking person.
Original: In the Catholic Church and the Anglican Communion , he is a saint and pre-eminent Doctor of the Church , and the patron of the Augustinian religious order ; his memorial is celebrated 28 August , the day of his death .
Simplified: In Roman Catholicism and the Anglican Communion , he is a saint and Doctor of the Church , and the patron of the Augustinian religious order .