someone who canbehave,work, andlivein a way thatseemsnormalalthoughthey areaddictedto(=unabletostopusing too much)alcohol,drugs, etc.:
She was ahighlysuccessfulathleteand afunctioningalcoholic.
What do you do if youdiscoverthatyourlovedone is afunctioningaddict?
Would you say he was a highfunctioningalcoholic?