Grammar: Infinitive

Revised as of
13 Feb 2023

The infinitive can be both easy and touchy to identify. You’d think it would be very simple what with to + infinitive, but sometimes that to is a preposition instead.

Besides the to version, there is also the infinitive + -ing version, which can be tricky to differentiate from the gerund or participle -ings.

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. . . an evolving list of the structural rules and principles that determines where words are placed in phrases or sentences as well as how the language is spoken. Sometimes I run across an example that helps explain better or another “also known as”. Heck, there’s always a better way to explain it, so if it makes quicker and/or better sense, I would appreciate suggestions and comments from anyone on an area of grammar with which you struggle or on which you can contribute more understanding.

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Infinitive
Definition: Verbal in its to form. To call, to eat, to drive, to play, to anything . . . NOTE: A present participle also uses a verb + -ing ending BUT is used as an adjective while the gerund uses a verb + -ing as a noun. POST CONTENTS: Differences Between Participles, Gerunds, and Infinitives Infinitive Marker Confusing Used To Construction Use the Too + Infinitive After certain verbs After adjectives too + adjective adjective + enough Use the Infinitive + -ing After Certain Verbs After a Preposition When Subject of a Clause Use Either To or -ing Infinitive Phrase Split Infinitives
Infinitive vs Gerund vs Participle:
The main problem is that participles and gerunds look alike, especially in their -ing form. It’s all the fault of those 18th century grammarians who finally settled down to make sense of the English language. You can see how much success they had, lol. Seriously, though they did do a great job with what they had at the time. Latin was the classic language at the time, and this is where those linguists started. Gerunds and participles were treated differently in Latin, which is why they’re thought of as different now. Today’s grammarians are beginning to refer to them as gerund-participles. It’ll take awhile for this concept to catch on, so it’s important that writers today know what the current differences are. I know . . . it’s a pain. Return to top or post contents
The difference is that:
Verb	What It Does	Examples
Gerund	Functions as a noun Always has an -ing ending	Hiking is a favorite sport in Colorado. After running into Helen, George knew it meant a three-hour lunch.
Infinitive	Base form of a verb, to ___, that functions as an adjective, adverb, or noun	She had a gift to give me. She wanted to buy the hat. Jamie likes to hike.
Participle Return to top or post contents	Functions as an adjective Depending on tense, it may have an -ing or -ed [+] ending	He had hiked to Pike’s Peak. Running into Helen meant a three-hour lunch. Jamie’s snoring was enough to keep Marge awake all night.
Infinitive Marker
Definition: To is the word which can “mark” a verb as an infinitive. CAUTION: To can also mark a preposition. Rule: When to is followed by the verb in its base or simple present form, then it’s an infinitive marker. If to is followed by the verb as a gerund or participle, then it’s a preposition.
To as Infinitive Marker To as Preposition I am going to hang this lamp. I’m looking forward to hanging this lamp at last. I want to swing from this tree. I went from dancing to swinging from this tree.
Exceptions: The construction surrounding used to can be confusing. Barbara suggested a way to determine when an infinitive OR a preposition follows used to.
I used to DO something I am used to something When I was a student, I used to cook my own food. Now I am used to cooking for a big family. I used to play outside from first light to darkest night. I am used to playing outside. I used to read for hours. I am used to reading for hours. I used to hate doing dishes. I am used to having to do the dishes. Legend: Yellow indicates the past tense verb Green indicates the infinitive Orange indicates the phrasal verb ending with a preposition Blue indicates the verbal noun
Use the To + Infinitive
After Adjectives	Rule: Always use an infinitive after adjectives.
Return to top or post contents	Partial List of Adjectives
	disappointed glad happy relieved sad surprised
	Examples:
	Legend: Yellow indicates the adjective Green indicates the infinitive I was happy to help them. She will be delighted to see you.
too + adjective . . .	Rule: . . . is followed by the to + infinitive.
Return to top or post contents	Legend: Yellow indicates the adjective Green indicates the infinitive The water was too cold to swim in. My tea is too hot to drink.
adjective + enough . . .	Rule: . . . is followed by the to + infinitive.
Return to top or post contents	Legend: Yellow indicates the adjective + enough Green indicates the infinitive He was strong enough to lift it. She is rich enough to buy two.
After Certain Verbs	Rule: Always use a to + infinitive after certain verbs.
Return to top or post contents	Partial List of After Verbs agree allow can / can’t afford choose decide encourage expect forget help hope learn manage mean need offer pretend promise refuse teach train want would like
	Examples:
	Legend: Yellow indicates the after verb Green indicates the infinitive I forgot to close the window. Mary needs to leave early. Why are they encouraged to learn Spanish? We can’t afford to take a long holiday.
Use the Infinitive + -ing
After Certain Verbs	Rule: Always use an infinitive -ing after certain verbs.
Return to top or post contents	Partial List of Certain Verbs
	avoid dislike enjoy finish give up mind not mind practice
	Examples:
	Legend: Yellow indicates the “certain” verb Green indicates the infinitive I dislike getting up early. Would you mind opening the window?
After a Preposition	Rule: Always use an infinitive -ing after a preposition.
Return to top or post contents	Legend: Yellow indicates the preposition Green indicates the infinitive + -ing I look forward to meeting you. They left without saying goodbye.
When Subject of a Clause	Definition: An infinitive clause that is a dependent clause whose verb is in the infinitive form. It may have a subject, object, complement, or modifier. NOTE: They are not introduced by a subordinating conjunction. A.k.a. infinitival clause, infinitive clause, to-infinitive clause Credit to: Nordquist Rule: Always use an infinitive -ing when it is the subject of a clause.
Return to top or post contents	Legend: Green indicates the subject infinitive + -ing Swimming is good exercise. Doctors say that smoking is bad for you.
Use Either to or -ing	Rule: Occurs when a “verb can be followed by the -ing form (gerund) or the to form (infinitive) without a big change in meaning” (Infinitive).
Return to top or post contents	Partial List of “Certain” Ambivalent Verbs
	begin continue hate intend like love prefer propose start
	Examples:
	It began to sleet. It began sleeting. I prefer to paint landscapes. I prefer painting landscapes. Legend: Yellow indicates the “certain” verb Green indicates the to + infinitive Pale green indicates the infinitive + -ing
Infinitive Phrase	Rule: Consists of an infinitive — to + verb + any modifiers or complements associated with it. Infinitive phrases may act as adjectives, adverbs, and nouns.
Return to top or post contents	Legend: Green indicates the infinitive phrase Her move to California wasn’t turning out as she thought. She wanted to wear the red dress. His plan to play bingo and get cozy with Martha was doomed.
NEVER Split an Infinitive	Definition: Splitting an infinitive simply means that another word has been inserted between the to and the infinitive (the verb).
	“To boldly go where no man has gone before” is the most frequently cited example of a split infinitive. Rule: For generations, we’ve been told to “never split an infinitive”, primarily because of those Latin construction rules 18th century grammarians used as the basis to bring order to the English language. As we all know, rules are made to be broken, and this is definitely one of them. The one rule you may never break is making it hard for your reader to understand what you’re saying. If you’re in doubt, keep the to and the infinitive together. Exception may occur in informal writing when a single adverb splits the infinitive as in the example below and the Star Trek quote on the right (OWL).
	YES NO Jerry asked us to plan more carefully and specifically than in the past for a hostile takeover. Jerry asked us to more carefully and specifically than in the past plan for a hostile takeover. Formal Informal I needed to gather my personal possessions quickly. I needed to quickly gather my personal possessions. We had to more than triple the number of screws we used.

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Resources for Infinitive

Barbara. “To as a Marker for an Infinitive vs. To as a Preposition.” Pearson Longman. <http://www.pearsonlongman.com/ae/azar/grammar_ex/message_board/archive/articles/00069.htm>.

“Infinitive or -ing?” English Club. n.d. Web. n.d. <https://www.englishclub.com/grammar/verbs-m_infinitive-ing.htm>.

Nordquist, Richard. “Infinitive Clauses.” ThoughtCo. 29 Mar 2018. Web. 13 Feb 2023. <https://www.thoughtco.com/infinitive-clause-grammar-1691062>.

Purdue OWL. Purdue University. n.d. Web. n.d. <https://owl.english.purdue.edu/owl/resource/627/03/>.

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Pinterest Photo Credits

Giovanni Mongiano by Paola Vigna under the CC BY-SA 4.0 license, via Wikimedia Commons is a cropped and flipped derivative.