Diagramming sentences helps reveal the structure of the English language because a diagram places every word in a sentence in its own position. The ability to diagram helps students visualize the ways parts of speech work in a sentence and see grammar rules, which helps improve their writing skills.

The best way to approach diagramming is to first identify each word in the sentence’s part of speech and function. Some important parts of speech to identify are listed below:

Noun-a person, place, thing, or idea (proper nouns are capitalized and include names and places)

Subject-a noun or noun phrase (a noun and its modifiers) that indicate what the sentence or clause is about or who performs the action

Adjective-a word that modifies (describes) a noun

Verb-a word that describes an action, state, or occurrence, an action verb shows the action the subject takes and a linking verb connects the subject with an adjective or noun that identifies the subject

Adverb-modify verbs, adjectives, or other adverbs

Subject Complement-a word that renames or modifies the subject (examples: predicate nominative, predicate adjective, direct object, and indirect object)

Predicate Nominative-object of a linking verb, a noun that refers back to the subject of the sentence

Predicate Adjective-object of a linking verb, an adjective that describes the subject of the sentence

Direct Object-object of an action verb, receives the action of the verb

Indirect Object-tells to whom or for whom the action of a sentence is done, receives the direct object

Preposition-a word that expresses relation between words or elements in a sentence or clause (Examples: above the sky, in my pocket, to my school)

Prepositional Phrase-a preposition and its object and any modifiers

Participle-the -ing and -en form of a verb functioning as an adjective or adverb

Gerund-An -ing verb functioning as a nominal

Relative Clause-a clause introduced by the relative pronoun (who, which, that) or a relative adverb (when, where, why) that modifies a noun in the main clause

Step 1: Locate the Subject and Verb

First, start with the key elements, the subject and verb. Every sentence must have a subject and verb, an action and someone or something performing the action. The subject will take the first position on the diagram and the verb will take the second position, as seen in Figure 1.

Step 2: Determine the Type of Verb

Verbs can either be categorized as action verbs or linking verbs. Action verbs are used when the subject is doing something, such as running, singing, or thinking. Linking verbs are most commonly “be” verbs, such as am, was, are, or is.

It is important to differentiate between the two types of verbs because action verbs take direct objects and linking verbs can have either predicate nominatives or predicate adjectives.

Direct objects, predicate nominatives, and predicate adjectives all are placed in the third position on the diagram, separated by a line that does not intersect the main line, as seen in Figure 2.

There is a difference between diagramming a direct object and a predicate nominative. The line between the second and third positions when a predicate nominative or predicate adjective is present is slanted towards the subject because they refer back to the subject, like in the third example in Figure 2.

Step 3: Check for Indirect Objects

Indirect objects are present when there is an action verb and a direct object. They can be located in a sentence by asking the question, "for whom?" after the verb. The indirect object is placed on a "swing" under the verb in a diagram, as seen in Figure 3.

Step 4: Place Modifiers on the Diagram

Modifiers, such as adjectives and adverbs, are placed on a slanted line underneath the word they describe, as seen in Figure 4. Adjectives modify nouns and adjectives modify adjectives, verbs, and other adverbs.

Step 5: Diagram Compounds

Each position in the sentence, including the subject, verb, and subject complement position, can contain compounds, which means there can be two or more words in the same position functioning the same in the sentence.

Figure 5A shows a compound subject and Figure 5B shows a compound verb with respective direct objects. To diagram this, the main line of the diagram splits to form two lines, with the conjunction "and" on a dotted line joining the two. The sentence is diagrammed as normal after creating the split.

Step 6: Identify Prepositional Phrases

Prepositional phrases can either be adjectival and modify nouns or adverbial and modify verbs, adjectives, or other adverbs. The best way to identify prepositional phrases is by knowing standard prepositions, such as in Figure 6A.

Adjectival prepositional phrases usually answer the question “what kind?” Adverbial prepositional phrases usually tell “when,” where,” or “how.”

On a diagram, prepositional phrases are placed on a swing under the word they modify, as seen in Figure 6B. The preposition is placed on the slanted part of the swing and the object of the preposition is placed on the straight line after it. The modifiers of the object should be placed under it.

Step 7: Identify Participles

Participles are verb forms acting as adjectives. The present

participle is in the “-ing” form of the verb.

Like in Figure 7, they will be placed on a swing, curved from the slanted part to the straight line, under the noun they modify.

Step 8: Identify Gerunds

Gerunds function as nouns and can fill the first or third position of a diagram as a subject or subject complement. They can also act as the object of a preposition. Gerunds can be identified because they are in the -ing form of the verb.

On a diagram, gerunds are indicated by a "stair step" form, as shown in Figure 8 in front of the word "being." They are raised on the diagram in the position they fill. In Figure 8, "Being in a band" is acting as the subject, so it fills the first slot.

Step 9: Identify Relative Clauses

The relative pronoun or adverb are diagrammed as they function in their own sentence. In Figure 9, "who" describes James in the main clause but acts as a subject in its own clause. However, they are connected to the word in the main clause that they modify with a dotted line.