*Arabic: ''Sayidna'' (literally "our master," also Latinized as ''Sayedna'')
Father, either by itself or followed by the priest's name
. Unless you know differently for a particular priest, it would be normal to use his full christian name (do not shorten it): ''Father Andrew'' is preferable to ''Father Andy'' etc. ''Father'' should not be followed by a surname as a greeting.
It is not correct to call a deacon ''Father'' unless he is also a monk. This is, however, widely ignored and ''Father'' is very common. Deacon, either followed by his Christian name or by itself is correct.