IPA: //ˈpɒlɪˌhɪstər//
KK: /pɑˈlɪhɪstər/
A person who has a wide range of knowledge in many different subjects.
The polyhistor was invited to speak at the conference due to his expertise in various fields.
Polyhistor → It is formed from "poly-" (from Greek "polus", meaning many) and "histor" (from Greek "histor", meaning learned or wise). The word "polyhistor" refers to a person who is knowledgeable in many fields or subjects.
Think of someone who is 'wise' ('histor') in 'many' ('poly') areas of knowledge — that's what a polyhistor is.
No commonly confused words.