A split infinitive is a structure in which an adverb is put between 'to' and the infinitive of a verb, as in 'to really experience it'. Some people think it is incorrect to use split infinitives.
split infinitive in British English
noun
(in English grammar) an infinitive used with another word between to (the infinitive marker) and the verb itself, as in I want to really finish it this time
▶ USAGE The traditional rule against placing an adverb between to and its verb – 'splitting the infinitive' – is gradually disappearing. Although itis true that a split infinitive may result in a clumsy sentence (he decided to firmly and definitively deal with the problem), this is not enough to justify the absolute condemnation that this practice hasattracted. Indeed, very often the most natural position of the adverb is between to and the verb (he decided to really try next time) and to change it would result in an artificial and awkward construction (he decided really to try next time). The current view is therefore that the split infinitive is not a grammatical error.Nevertheless, many writers prefer to avoid splitting infinitives in formal writtenEnglish, since readers with a more traditional point of view are likely to interpretthis type of construction as incorrect
split infinitive in American English
Grammar
an infinitive with an adverb or other modifier placed between to and the verb form (Ex.: he decided to gradually change his methods): although some object to this construction, many writers use split infinitives where ambiguity or wrong emphasis would otherwise result