How to spell INFESITVE correctly?

The correct spelling for "infesitve" is "infinitive". The infinitive form of a verb is the base form preceded by the word "to". Some examples of infinitive verbs are "to run", "to play", and "to sing". Other commonly misspelled words related to grammar include "affect" and "effect", "there", "their", and "they're", and "your" and "you're."