What is an infinitive particle?

Answer 1

"to" as in "To err is human." It turns a verb into a noun or adverb. It works similar to a gerund, which is formed by adding -ing, as in "Erring is human." A split infinitive occurs when there are words between "to" and its verb, for example "to boldly go where no man has ever gone before."

Answer 2

An infinitive particle is a word that is used before an infinitive verb to indicate a specific grammatical or semantic function. In English, "to" is the infinitive particle (e.g., to run, to play). In other languages, such as Spanish or French, infinitive particles can vary.