Split infinitive

In the English language, a split infinitive or cleft infinitive is a grammatical construction in which a word or phrase comes between the to and the bare infinitive of the to form of the infinitive verb. Usually an adverb or adverbial phrase comes between them.

A well-known example occurs in the opening sequence of the Star Trek television series: to boldly go where no man has gone before; the adverb boldly is said to split the infinitive to go. Sometimes more than one word splits the infinitive , as in: The population is expected to more than double in the next ten years.

In the 19th century, some grammatical authorities sought to introduce a prescriptive rule against it. The construction is still the subject of disagreement: "No other grammatical issue has so divided English speakers since the split infinitive was declared to be a solecism in the 19c [19th century]: raise the subject of English usage in any conversation today and it is sure to be mentioned." Most modern English usage guides have dropped the objection to the split infinitive.