IPA: /nɪˈɡoʊʃieɪtə/
KK: /nɪˈɡoʊʃiˌeɪtər/
A person who discusses and arranges agreements between two or more parties.
The negotiator worked hard to reach a compromise that satisfied both sides.
Negotiator → It is formed from "negotiari" (meaning to carry on business) and the suffix "-or" (meaning one who). A negotiator is one who carries on business or discussions to reach an agreement.
Think of someone who is 'carrying on business' — that's what a negotiator does, facilitating discussions to reach agreements.