Who is “faithful”?

The Roman Catholic church uses the term faithful to designate its members, i.e. those who have been baptized using the procedure recognized by Roman Catholic church. ([CIC1983], 204)

I try to avoid this meaning of the word because it is offending other Christian denominations or people who declare to believe in the Gospel but refuse to join some concrete church institution.

The official French translation of faithful is fidèle (loyal). That’s more understandable. The German translation der Gerechte (German) sounds weird.

Christians can indeed use the word faith to designate the faith in the Gospel. For Christians, a faithful is a human who “understood” the Good News and “decided” to believe in it.[1] Also other religious institutions use the word “faithful” in that specific meaning of belief in their specific teachings. But this usage becomes questionable in multicultural contexts because it assumes that there is one “right” religion.