IPA: /ˈmɔːrnər/
KK: /ˈmɔrnər/
A person who feels or shows sadness, especially because someone has died.
The mourners gathered at the cemetery to pay their respects.
Mourner → It is formed from "mourn" (from Old French *morir*, meaning to grieve or feel sorrow) and "-er" (meaning a person who). A mourner is a person who expresses grief or sorrow, especially at a funeral.
Think of someone who is 'grieving' ('mourn') and the '-er' indicates that this person is actively expressing that grief.