How does ed differ from impotence?

Same thing: Erectile dysfunction is medical term for impotence which is defined as inability to attain & sustain an erection adequate for penetration leading to distress. So if it doesn't bother you, it's not ed. But let's also be realistic in that our refractory period (time between having an orgasm and attaining another erection) increases w/age, so don't claim ed if you can't have sex 5x/d @ 99yo like 18yo.