noun

a traditional and widely accepted way of behaving or doing something that is specific to a particular society, place, or time.

the old English custom of dancing round the maypole

tradition,practice,usage,observance,way,convention,procedure,ceremony,ritual,ordinance,form,formality,fashion,mode,manner,shibboleth,sacred cow,unwritten rule,mores,way of doing things,consuetude,praxis

adjective

made or done to order; custom-made.

a custom guitar