IPA: /ˈɛstrændʒər/
KK: /ˈɛstrændʒər/
A person who causes someone to feel distant or alienated from others.
The estranger in the story made the main character feel isolated from her friends.
Estranger is derived from Old French 'estranger' (meaning to be a stranger or foreigner), which comes from the Latin 'extraneus' (meaning external or foreign). The word refers to someone who is from outside a particular place or group.
Think of someone who is 'external' ('extraneus') to a group — that's why 'estranger' means a stranger or foreigner.