/ əbˈzɜːvəns; NAmE -ˈzɜːrv-/ noun
1.
[ U , sing. ] the practice of obeying a law, celebrating a festival or behaving according to a particular custom :
observance of the law
a strict observance of the Sabbath
OPP non-observance
2.
[ C , usually pl. ] an act performed as part of a religious or traditional ceremony :
religious observances
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WORD ORIGIN
Middle English : via Old French from Latin observantia , from observant- watching, paying attention to, from the verb observare to watch, from ob- towards + servare attend to, look at.