The Buddha explains the three types of feelings and their impermanent nature.
“Tisso imā, bhikkhave, vedanā aniccā saṅkhatā paṭiccasamuppannā khayadhammā vayadhammā virāgadhammā nirodhadhammā. Katamā tisso?
“Bhikkhus, these three feelings are |impermanent::not lasting, transient, unreliable [anicca]|, |constructed::compounded, conditioned, fabricated [saṅkhata]|, |dependently arisen::casually produced, arisen together from a cause [paṭiccasamuppanna]|, naturally wearing away, subject to disintegration, subject to fading away, having the nature to end. What three?
Sukhā vedanā, dukkhā vedanā, adukkhamasukhā vedanā— imā kho, bhikkhave, tisso vedanā aniccā saṅkhatā paṭiccasamuppannā khayadhammā vayadhammā virāgadhammā nirodhadhammā”ti.
Pleasant feeling, painful feeling, and neither-painful-nor-pleasant feeling. These, bhikkhus, are the three feelings that are impermanent, constructed, dependently arisen, naturally wearing away, subject to disintegration, subject to fading away, having the nature to end.”
“Bhikkhus, these three feelings are |impermanent::not lasting, transient, unreliable [anicca]|, |constructed::compounded, conditioned, fabricated [saṅkhata]|, |dependently arisen::casually produced, arisen together from a cause [paṭiccasamuppanna]|, naturally wearing away, subject to disintegration, subject to fading away, having the nature to end. What three?
Pleasant feeling, painful feeling, and neither-painful-nor-pleasant feeling. These, bhikkhus, are the three feelings that are impermanent, constructed, dependently arisen, naturally wearing away, subject to disintegration, subject to fading away, having the nature to end.”
“Tisso imā, bhikkhave, vedanā aniccā saṅkhatā paṭiccasamuppannā khayadhammā vayadhammā virāgadhammā nirodhadhammā. Katamā tisso?
Sukhā vedanā, dukkhā vedanā, adukkhamasukhā vedanā— imā kho, bhikkhave, tisso vedanā aniccā saṅkhatā paṭiccasamuppannā khayadhammā vayadhammā virāgadhammā nirodhadhammā”ti.