Question

to be fair, sauna etiquette varies hugely between countries.
in this sentence, etiquette means:

• rules governing socially acceptable behavior
• a firm rebuke
• an essay or article that gives a critical evaluation
• an unproved statement advanced as a premise in an argument

Explanation:

The word "etiquette" generally refers to social - norms and rules of behavior. In the context of sauna etiquette varying between countries, it means the rules governing socially acceptable behavior in saunas.

Answer:

rules governing socially acceptable behavior