observance

英[əb'zɜːv(ə)ns] 美[əb'zɝvəns]

1. the act of observing; taking a patient look

2. a formal event performed on a special occasion;

"a ceremony commemorating Pearl Harbor"

3. the act of noticing or paying attention;

"he escaped the notice of the police"

4. conformity with law or custom or practice etc.