Gerunds, Infinitives, and Verbs-as-Nouns

In my last post about gerunds (verbs with in “-ing”) and infinitives (verbs that follow “to…”), I showed you how to use these verb forms to describe an action.

Gerunds and infinitives are also commonly used in verbs that have been turned into nouns. This may sound a little strange. How does a verb turn into a noun? Allow me to explain.

Usually, a verb is used to describe what the subject of a sentence does. Examples of sentences with this pattern include “Cats like mice” and “Cats like chasing mice.” In the second sentence, “like” is the main verb, and “chasing” is the action being described. But both like and chasing describe what the cats, the subject of the sentence, do.

However, at other times, a verb can actually be the subject of a sentence or clause. When this happens, the verb behaves like a noun. Let’s look at some examples of this, with explanations.

  • To start a fire is difficult if there are no matches.
    • Explanation: Here the verb start has been put into the phrase to start a fire. Because to start a fire is at the beginning of the sentence, and is followed by the verb is and the adjective difficult, to start a fire behaves like a noun phrase. You could substitute other noun phrases for to start a fire and the sentence would still have correct grammar. For example, you could say This test is difficult or English is difficult.
  • Starting a fire is difficult if there are no matches
    • Explanation: Like in the previous example sentence, the verb start is the main word in the noun-phrase subject of the sentence.
  • Everyone knows that starting a fire is difficult if there are no matches.
    • Explanation: In this sentence, the verb start is the subject of the clause starting a fire is difficult if there are no matches. Everyone is the subject of the sentence as a whole.
  • Everyone knows that to start a fire is difficult if there are no matches.
    • Explanation: This sentence follows the exact same pattern as the previous example, with a verb as the subject of the clause. However, in this case, the verb start is an infinitive instead of a gerund.

These example sentences are all very similar, except that two of them use an infinitive and two use a gerund. How do you know when to use a gerund or an infinitive in the subject of a sentence or clause? Don’t worry, the answer to this is simple. See Rule 4 below! (Rules 1-3 of gerund/infinitive use can be found in my previous post Gerunds, Infinitives, and Describing Actions.)

Rule 4) When using a verb in the subject of a sentence or clause, you can use either a gerund or an infinitive

Practice for your TOEFL exam with Magoosh.

Example A: To build a house takes a long time.
Example B: Building a house takes a long time.
Example C: I am aware that to build a house takes a long time.
Example D: I am aware that building a house takes a long time.

Explanation: In each sentence, the verb build is the main word in the subject of either the whole sentence or a clause in the sentence. As part of a noun phrase subject, build can be formed either as gerund building or infinitive to build.

A verb can also be turned into a noun when it is the object of a preposition. I’ll give you a couple of examples below, again with explanations.

  • She finds enjoyment in singing.
    Explanation: The verb sing is the object of the preposition in.
  • She thinks of reading books as fun.
    Explanation: The verb read is the main word in the verb phrase reading books which is the prepositional object for of.

At this point, you may have already guessed the rule for using gerunds or infinitives in prepositional phrases:

Rule 5) If a verb is a prepositional object, it should be a gerund, not an infinitive.

Example: You may be thinking about taking the TOEFL exam.

Explanation: As part of the larger verb phrase taking the TOEFL exam, the verb take is the prepositional object of the preposition about. As a prepositional object, take must be expressed as the gerund taking.

So there you have it! Between this post and the last one, you have all the rules you need for common uses of “-ing” and “to…” verbs. In my next post on this subject, you’ll have a chance to do some review activities with these forms.


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  • David Recine

    David is a Test Prep Expert for Magoosh TOEFL and IELTS. Additionally, he's helped students with TOEIC, PET, FCE, BULATS, Eiken, SAT, ACT, GRE, and GMAT. David has a BS from the University of Wisconsin-Eau Claire and an MA from the University of Wisconsin-River Falls. His work at Magoosh has been cited in many scholarly articles, his Master's Thesis is featured on the Reading with Pictures website, and he's presented at the WITESOL (link to PDF) and NAFSA conferences. David has taught K-12 ESL in South Korea as well as undergraduate English and MBA-level business English at American universities. He has also trained English teachers in America, Italy, and Peru. Come join David and the Magoosh team on Youtube, Facebook, and Instagram, or connect with him via LinkedIn!

One Response to Gerunds, Infinitives, and Verbs-as-Nouns

  1. Chhaihour May 22, 2019 at 1:10 am #

    Thank you so much for explaining the differences between Gerund and To infinitive.

    Hello from Cambodia!

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