cleft infinitive
Definition - Another name for the split infinitive, i.e. an infinitive that has an adverb between the to and the verbal part.

Example -
In the phrase to boldly split, the infinitive is to split and boldly is the adverb that splits it.

Oxford English Dictionary -
The term's first citation is from 1893:
"My paper on the cleft infinitive, printed in the American Journal of Philology."
(F. Hall in Nation (N.Y.) LVI. 274/2)

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