Qual è la differenza tra grief, sorrow, mourning e aggravation? e Is it possible to use 'regret' as a synonym for any of these words? ?Sentiti libero di rispondere con un esempio.

@KatyaMo mourning primarily refers to the outward things that a person does when someone has died. So for instance, wearing black clothes or crying at the funeral.
Grieving is the emotion that a person feels when someone has died.

As nouns the difference between grief and sorrow is that grief is suffering, hardship while sorrow is (uncountable) unhappiness, woe

Aggravation :The feeling of impatience or anger caused by another's repeated disagreeable acts. Grief is a synonym of aggravation in irritation topic. Sometimes you can use "Grief" instead a noun "Aggravation", when it comes to topics like annoyance.

Dear me,what a big paragraph.hope it helps🙂