split infinitive

A to-infinitive with a word or phrase between to and the verb.

Split an infinitive when that placement makes the meaning clearer or the wording more natural. The construction is standard English: to fully recover, to carefully consider the alternatives. The infinitival marker to is a separate word, and English grammar does not require it to stand immediately beside the verb. Do not rearrange a clear sentence merely to avoid a split.

Placement and meaning. Place an adverb where its grammatical attachment and scope are clear. In The landlord promised to promptly repair the heater, promptly modifies the repair. Moving the adverb before to, as in The landlord promised promptly to repair the heater, makes it modify promised instead. An edit made solely to avoid a split can therefore change the meaning or introduce ambiguity.

An unsplit construction can be equally clear: She agreed to review the contract carefully. Neither placement is inherently superior. Choose the order that expresses the intended meaning without awkwardness.

A degree phrase can require a split infinitive: The theater needs to more than break even this season. Here more than modifies break even: revenue must exceed costs, not merely equal them. The phrase cannot follow break even with that meaning, and to break more than even is not standard English. The sentence could be recast with to earn a profit, but a split infinitive that is grammatical needs no such repair.

Length and interruption. Judge an intervening element by its kind, not its length. An adverb or adverb phrase such as fully or almost completely sits naturally between to and the verb. An element set off by commas, such as a parenthetical phrase or a clause, interrupts the infinitive and leaves the reader waiting for the verb. Move it outside the infinitive, and check that the revision preserves the original meaning.

Auxiliaries. An adverb between an auxiliary and a participle does not split an infinitive: to be fully refunded, to have quietly resigned. Here to stands next to its infinitive, be or have, and the adverb modifies the participle that follows. The position after the auxiliary is the standard one for such adverbs, so these constructions need no revision.

Negative infinitives. Use not to for ordinary negation: She chose not to reply. To not is grammatical, but not to is the standard order.

Examples

Use The council voted to quickly close the bridge. (Between to and close, quickly can modify only the closing. In voted quickly to close the bridge, it could describe the vote instead.)

Use The technician needs to completely disconnect the power supply. (Completely stands next to disconnect, the verb it modifies.)

Use Every sample is to be carefully labeled before shipment. (To immediately precedes be, so the infinitive is not split. Carefully modifies the labeling.)

Use We agreed not to release the findings before the review was complete. (Not to is the standard order for ordinary negation.)

Avoid We intend to, regardless of whether the supplier agrees to a discount, replace the equipment. (The clause beginning regardless interrupts the infinitive to replace and leaves the reader waiting for the verb. Write We intend to replace the equipment regardless of whether the supplier agrees to a discount.)

Split infinitives have occurred in English since the Middle English period. The prohibition became prominent in the nineteenth century, but it was never a rule of English grammar. Many people still object to the construction, but the objection has no grammatical basis.