Learning to use the "-ing," the infinitive ("to" + base form of the verb), and the past participle (in regular verbs, this is formed by adding "-ed" to the end of the verb) verb forms correctly can be challenging. When do you use "finishing" versus "to finish" versus "finished"? The information on this page can help.

To find more information about when to use an "-ing," an infinitive, or a past participle, look up the word in an online dictionary such as Merriam Webster, or use a corpus, such as The Corpus of Contemporary American English. Although there are some rules to follow, some of them simply have to be memorized.

Here are six common uses of the "-ing" form:

1. The "-ing" form is used in progressive verb tenses with auxiliary verbs (helping verbs). These are in active voice. Here are some examples:

• I am doing my homework.
• I have been writing all day.
• I was writing when the pizza arrived.

2. The "-ing" form can function as a noun. These nouns are called gerunds and can be the subject of a clause, followed by a third-person singular (he/she/it) form of the verb. The gerund in the following sample sentences is bolded, and the verb is italicized:

• Writing is an important skill.
• Hiking is one of my favorite activities.
• Reading before bed helps me fall asleep.

3. The "-ing" noun (or gerund) can be the direct object of certain verbs. Some verbs that are followed by a gerund are the following:

• Admit
• Avoid
• Consider
• Deny
• Discuss
• Practice
• Recall
• Suggest

The verb in the following sample sentences is italicized, and the gerund is bolded:

• He often avoids answering his phone.
• I considered conducting semistructured interviews.
• She suggested taking notes.

4. The "-ing" form is used after a preposition. The preposition in the following example sentences is italicized, and the "–ing" is bolded:

• Before conducting the research, it is necessary to complete a literature review.
• Her experience in interviewing will be beneficial.
• He is bad at remembering appointments. 
• They complained about driving in rush hour.

5. Adjectives are sometimes formed using "-ing". The "-ing" in the following example sentences is bolded:

• I read an interesting book.
• The barking dog was annoying.

6. The "-ing" form is sometimes used to include additional information in a sentence in a reduced relative clause. The "-ing" in the following example sentences is bolded, and the full relative clause is italicized:

• The woman wearing a dress is sitting by the window. (The woman who is wearing a dress is sitting by the window.)
• The pens sitting on the desk belong to the teacher. (The pens that are sitting on the desk belong to the teacher.)

Here are four common uses of infinitives ("to" + base form of the verb):

1. The infinitive is required after certain verbs in English. Some verbs that take an infinitive following them are the following:

• Agree
• Choose
• Claim
• Decide
• Expect
• Manage
• Need
• Offer
• Plan
• Prove
• Refuse
• Want
• Wish

The verb in the following example sentences is italicized, and the infinitive is bolded:

• I decided to go to a movie.
• He expected to obtain reliable results.
• She offered to help.

2. The infinitive is also used after certain verb + direct object structures. Some verbs that use this pattern are the following:

• Advise
• Allow
• Ask
• Encourage
• Help*
• Need
• Persuade
• Require

In the following example sentences, the verb is italicized, the direct object is bolded and italicized, and the infinitive is bolded:

• I advised him to stay. ("Him" is the direct object here.)
• I encouraged the participants to ask questions. ("Participants" is the direct object here.)
• She required us to sign the consent form. ("Us" is the direct object here.)
• He helped me to learn to read. He helped me learn to read. (With the verb "help," the infinitive can be used with or without "to." "Me" is the direct object here.)

3. Infinitives are used after certain adjectives. Some adjectives that are followed by infinitives are the following:

• Difficult
• Easy
• Impossible
• Wrong

The adjective in the following example sentences is italicized, and the infinitive is bolded:

• It was difficult to complete the rough draft.
• She thought it was impossible to remember all the rules.
• I was wrong to assume you did not understand.

4. Infinitives are used to express purpose (in order to do something).  The infinitive in the following sample sentences is bolded:

• She is driving quickly (in order) to arrive on time.
• He completed all his homework (in order) to earn a good grade.
• I rewrote my draft three times (in order) to revise it the best I could.

Some verbs can be followed by either a gerund or an infinitive and the meaning of the sentence does not really change:

• Begin
• Continue
• Hate
• Like
• Love
• Start

The verb in the following example sentences is italicized, and the infinitive or gerund is bolded:

• She likes to read.
• She likes reading.

• He started to learn how to swim.
• He started learning how to swim.

However, for some other verbs that can be followed by either a gerund or infinitive, the choice of the gerund or infinitive creates a difference in meaning:

• Forget
• Remember
• Stop
• Try

The verb in the following example sentences is italicized, and the gerund or infinitive is bolded:

• I stopped smoking. (I no longer smoke.)
• I stopped to smoke. (I stopped someplace along the way to smoke.)

• He did not remember going to the store. (He went to the store, but he did not recall that he had been there.)
• He did not remember to go to the store. (He intended to go to the store, but he did not do it.)

In a regular verb, the past participle is formed by adding "-ed". However, there are many irregular verbs in English, and these past participle forms must be memorized. Here are four common uses of past participles:

1. The past participle is used with "have" auxiliaries (helping verbs) in active voice. The "have" auxiliary in the following example sentences is italicized, and the past participle is bolded:

• She has completed her degree.
• She had completed her degree before being hired.
• I have finished my homework.
• I had finished my homework before going to the movie.

Also see this link on verb tenses for more examples.

2. The past participle is used after "be" auxiliaries in passive voice. Be sure to check our webpage on the appropriate use of passive voice in scholarly writing. The "be" auxiliary in the following example sentences is italicized and the past participle is bolded:

• I was born in 1976.
• Hamlet was written by Shakespeare.
• The plates broke when they were dropped.

3. The past participle is sometimes used in a phrase to supply additional information. These participial phrases come from relative clauses with a passive meaning. The past participle in the following example sentences is bolded, and the full relative clause is italicized:

• The ideas presented at the conference are important to remember. (The ideas that were presented in the conference are important to remember.)
• The drinks served at that bar are delicious. (The drinks that are served at that bar are delicious.)
• Taken by surprise, Alice hugged her long lost friend. (Alice, who was surprised, hugged her long lost friend.) 

4. The past participle is sometimes used as an adjective. The past participle in the following example sentences is bolded:

• The received goods were damaged in shipping.
• She tried to repair her broken phone.
• The lost dog wandered the neighborhood.

Sometimes both the "-ing" and the past participle ("-ed") forms can function as adjectives. However, each form has a different meaning.  The "-ing" and the past participle is bolded in the example sentences below. Notice that the "-ing" adjective refers to a thing and the past participle ("-ed") adjective refers to a person.

• The ideas are exciting. (This refers to the ideas themselves.)
• He is excited. (This refers to the person.)

• The rules are confusing. (This refers to the rules themselves.)
• I am confused. (This refers to the person.)

• The conclusion to the movie was satisfying. (This refers to the movie.)
• I am satisfied with the results. (This refers to how I feel about the results.)