binding
Word family
Synonym discussion
Sense: adjective/1
All four words say that something must be obeyed, but they fit different situations. 'Binding' is the standard word for promises, contracts, and rulings: once it is signed, you cannot just back out. 'Enforceable' goes one step further — it stresses that a court could actually make you comply, so a 'binding' contract that is also 'enforceable' will hold up in court. 'Obligatory' is broader; it can describe duties that come from manners, religion, or work routines, not only law: morning meetings can be obligatory. 'Mandatory' usually points to rules set by an authority for everyone (a mandatory vaccine, mandatory training); it sounds firmer and more public than 'obligatory'. So you might say: 'The contract is binding, the clause is enforceable in court, attendance is obligatory, and the safety briefing is mandatory.'
Common collocations
Etymology
Binding comes from the Old English verb 'bindan', meaning to tie or fasten with rope or cord. The '-ing' ending turned the verb into a noun for the act of tying, and later for the thing that ties — first ropes and straps, then book covers from the 1300s, then sewn fabric edges. The adjective sense 'that must be obeyed' grew from the same image: a promise or law was felt to 'tie' the people who made it, just as a rope ties an object.