Sentence diagram

In pedagogy, a sentence diagram is a pictorial representation of the grammatical structure of a natural-language sentence. A sentence diagram is a form of a parse tree.


Most methods of diagramming are based on the work of Alonzo Reed and Brainerd Kellogg in their book Higher Lessons in English, first published in 1877, though the method has been updated with recent understanding of grammar.

Reed and Kellogg were preceded by, and their work probably informed by, W. S. Clark, who published his "balloon" method of depicting grammar in his 1847 book A Practical Grammar: In Which Words, Phrases & Sentences are Classified According to Their Offices and Their Various Relationships to Each Another. (For a discussion and description of Clark's balloon architecture, see Chapter 2 of Kitty Burns Florey’s book listed in Further Reading below.)

In recent years, the Reed-Kellogg system has somewhat fallen out of use among linguists. While some teachers continue to use the Reed-Kellogg system, others have discouraged it in favor of the tree diagram, which orders words differently. X-bar theory is considered to be a more accurate representation of the structures upon which the rules of natural-language syntax operate.

Reed and Kellogg defend their system in the preface to their grammar:

The Objections to the Diagram.--The fact that the pictorial diagram groups the parts of a sentence according to their offices and relations, and not in the order of speech, has been spoken of as a fault. It is, on the contrary, a merit, for it teaches the pupil to look through the literary order and discover the logical order. He thus learns what the literary order really is, and sees that this may be varied indefinitely, so long as the logical relations are kept clear.

The assertion that correct diagrams can be made mechanically is not borne out by the facts. It is easier to avoid precision in oral analysis than in written. The diagram drives the pupil to a most searching examination of the sentence, brings him face to face with every difficulty, and compels a decision on every point.

The Reed-Kellogg System

A simple sentence is shown as
  subject | predicate  
(Please be aware of the fact that the vertical line that divides the subject and the predicate does go through the horizontal sentence line.) for example:
  I | am  
The diagram of a simple sentence begins with a horizontal line called the base. The subject is written on the left, the predicate on the right, separated by a vertical bar which extends through the base. Please note that in the illustration above, the line does not run through the base line. This is incorrect – it makes the verb a direct object – and is done here only for technical reasons. The subject and predicate are separated by a vertical line that extends below the baseline. The predicate must contain a verb, and the verb requires, permits or precludes other sentence elements to complete the predicate. The verb and its object, when present, are separated by a line that ends at the baseline. If the object is direct or indirect, the line is vertical. If the object is a predicate noun or adjective, the line looks like a backslash, , sloping toward the subject.


Modifiers of the subject, predicate, or object are placed below the base line. Adjectives and adverbs (including articles) are placed on slanted lines below the word they modify. Prepositional phrases are also placed beneath the word they modify; the preposition goes on a slanted line and the slanted line leads to a horizontal line on which the object of the preposition is placed. Compound subjects, predicates, objects, etc. are drawn as multiple horizontal lines stacked vertically, joined at each end by a fan of diagonal lines; the coordinating conjunction goes on a vertical line through the left ends of the horizontal lines.

Prepositional phrases

Prepositional phrases consist of two lines: the preposition itself is drawn just as an adjective or adverb would, hanging down below the antecedent, and the complement is drawn on a line protruding horizontally from a point near the bottom of the thing


Compound sentences

Compound sentences are composed of two independent clauses connected by a coordinating conjunction. Each clause is diagrammed separately; the verbs of the two clauses are joined by a dotted line which goes vertically, then horizontally with the conjunction written on the line, and then vertically again.

Subordinate clauses

Subordinate clauses are connected to an independent clause by a subordinating conjunction. The subordinate clause is diagrammed separately, and the verbs of the two clauses are connected by a diagonal dotted line on which the subordinating conjunction is written.

Other structures


An appositive is written in parentheses, next to the word it describes.

Participles and participial phrases

A participle is given the same type of line as an adjective (see Modifiers, above), except that a small horizontal line branches off the end. The participle itself is written in a curved manner, so that the verb ending is written on the small horizontal line.

Any adjectives or prepositional phrases modifying the participial branch off of the small horizontal line, as if the participle were a noun.

Gerunds and gerund phrases

Gerunds are placed on a "staircase," which is then on a tower that has an upside down triangle base and a straight line going up to the staircase. The staircase is two steps, and the gerund should be placed onto it diagonally, as if it were resting full length on the stairs. The remaining parts of the gerund phrase follow it on a horizontal line connected to the edge of the "stairs."


An interjection is placed on a floating line separate to the rest of the sentence diagram.


Further reading

External links

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