obligatory

Obligatory describes something you do because you have to, not because you want to. When you buy a car, you have to fill out the obligatory forms. In many homes, saying please and thank you is obligatory.

Obligatory derives from the verb oblige, as in "after she was so nice, I felt obliged to take her a present." Some people feel burdened by lives of common obligation, giving presents, returning phone calls, eating birthday cake, attending religious services––none of which they feel any real desire to do.

Definitions of obligatory
1

adj required by obligation or compulsion or convention

“he made all the obligatory apologies”
Synonyms:
necessary
absolutely essential

adj morally or legally constraining or binding

“attendance is obligatory
“an obligatory contribution”
Synonyms:
bounden
morally obligatory
compulsory, mandatory, required
required by rule
de rigueur
required by etiquette or usage or fashion
imposed
set forth authoritatively as obligatory
incumbent on
morally binding or necessary
indispensable
unavoidable
prerequisite
required as a prior condition or course of study
necessary
absolutely essential
Antonyms:
optional
possible but not necessary; left to personal choice
elective
not compulsory
ex gratia
as a favor; not compelled by legal right
facultative
not compulsory
nonmandatory, nonobligatory
not required by rule or law
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