People rarely mean the same thing when they say "religion", nor do they realize that they don't mean the same thing.
For early Jews and Muslims, religion was law. For early Jews it was also tribal; for early Muslims it was universal. For the Romans religion was social events and festivals (law was separate ). For Jews today religion became ethnocultural, without the law --and for some, a nation. Same for Syriacs, Copts, and Maronites. For Orthodox and Catholic Christians religion is aesthetics, pomp and rituals. For Protestants religion is belief with no aesthetics, pomp or law. For Buddists/Shintoists/Hindus religion is philosophy. So when Hindu talk about the Hindu "religion" they don't mean the same thing to a Pakistani as it would to a Hindu, and certainly something different for a Persian.
People keep talking past each other. When the nation-state idea came about, things got more complicated. When an Arab now says "Jew" he largely means belief; a converted Jew is no longer a Jew. But for a Jew it means a nation.
In Serbia/Croatia, or Lebanon, religion means something at times of peace, and something quite different at times of war.