noun

an activity that is natural to or the purpose of a person or thing.

bridges perform the function of providing access across water

purpose,task,use,role,reason,basis,justification,responsibility,duty,concern,province,aim,activity,assignment,obligation,charge,chore,job,errand,mission,detail,undertaking,commission,capacity,post,situation,office,occupation,employment,business,operation,raison d’être,line of country,thing,bag,pigeon

verb

work or operate in a proper or particular way.

her liver is functioning normally

work,go,run,be in working/running order,operate,perform,be in action,be operative