How to Diagram Infinitive Verbs

Infinitive verbs can be many different parts of speech.

An infinitive is the word "to" followed by a verb. Infinitives look like verbs, but they are used as nouns, adverbs and adjectives in sentences. Because they can act like so many different parts of speech, they may appear in any part of a sentence. Figuring out which part of speech an infinitive is, in its context, is the key to diagramming it. When you know what function it serves in the sentence, you know where it belongs in your diagram.

Instructions

1. Identify the part of speech of the infinitive in the sentence. Is it a noun, an adverb, or an adjective? In the sentence "I want to eat your breakfast," "to eat" is the object of the verb "want," so it is a noun. In "I swim to relax," "to relax" modifies the verb "swim," so it is an adverb. In "The thing to try is dying your hair," "to try" describes the noun "thing," so it is an adjective.

2. Locate the place the infinitive belongs in your diagram. If it modifies another word, draw a diagonal line stemming from that word. Draw a horizontal line coming off the diagonal one, and leave space to write the infinitive on or above the horizontal line. If the infinitive is acting as a noun, either as the subject of the sentence or the object of the verb, draw a horizontal line in the subject or object position, leaving space to write the infinitive in that area.

3. Draw a short diagonal line in the space you have left for your infinitive. Write the word "to" on this line, then draw a horizontal line extending from it to its right, and write the verb there.

4. Add any modifiers the infinitive may have to the diagram. These modifiers create an infinitive phrase. For example, in "I want to eat your breakfast," "your breakfast" is part of the infinitive phrase. Diagram it into the infinitive phrase as though "eat" were a verb and "your breakfast" were its object, with a horizontal line extending to the right of "eat," "breakfast" written on that line, and "your" written on a diagonal line extending from "breakfast."

Tips & Warnings

• Do not confuse a prepositional phrase with an infinitive. If the word "to" is followed by a noun, it is a prepositional phrase. If it is followed by a verb, it is an infinitive.

References

• Grammar Revolution: Diagramming Verbals
• Diagram It!; Infinitives; Elizabeth O'Brien; June 2010

Resources

• Purdue Online Writing Lab; Infinitives; April 2010