Incorrect spelling


Incorrect spelling, explanation: there is no such form as invester, because the root word investire is Latin and to such words, we usually choose the suffix -or. Therefore investor is the correct form. -er can be used with many other words, for example, teacher, builder, but invester is an incorrect form.

Correct spelling


Correct spelling, explanation: in English, we create nouns, which relate to a person, by adding suffixes -er or -or. The latter is less often, and it usually is connected to the fact that it is used with words deriving from Latin. Therefore investor is the correct form as it comes from Latin investire. Invester is thus incorrect. The correct form is investor.

Definition of investor:
noun, someone who invests
He used to be a very successful stock investor, but he decided to retire.
Or investor is also an owner of a franchise restaurant in Florida.