observance

noun

1. (countable, uncountable)The practice of complying with a law, custom, command or rule.
2. (countable, uncountable)The custom of celebrating a holiday or similar occasion.
3. (countable, uncountable)Observation or the act of watching.
4. (countable, uncountable)A rule governing a religious order, especially in the Roman Catholic church.

   “Thomas Merton was a monk in the Order of Cistertians of the Strict Observance.”

5. (countable, uncountable)That which is to be observed.
6. (countable, uncountable)Reverence; homage.