Remember the definition of the infinitive form of a verb: the word you would ordinarily look up in the dictionary. Its bare form is just the word by itself: write. Its periphrastic form consists of the infinitive preceded by the preposition to: to write.
The bare infinitive appears in conjugations with the modal auxiliaries: I should write, I must write, I will write. The “to” form is needed for the modal ought: I ought to write.
But we’re not so interested in the use of infinitives to form certain conjugations. Instead, we want to see how they work on their own, as one of the three verbal phrases: infinitive, present participial, and past participial. The infinitive phrase gives us the ability to take a verb-like idea and use it as:
1. a noun 2. an adjective 3. an adverb
To increase the power of your prose, you must use infinitive phrases.
The Word to Introduces Infinitive Phrases
Just look at the four infinitive phrases in the preceding paragraph and the functions they perform:
|use of infinitives to form certain conjugations||adjective modifying use|
|we want to see how they work||noun, the direct object of want|
|the ability to take a verb-like idea||adjective modifying ability|
|To increase the power of your prose, you must use infinitive phrases.||adverb modifying must use|
to form certain conjugations
to see how they work (here the clause how they work acts as a noun)
to take a verb-like idea
to increase the power of your prose
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