Diagramming Sentences

Basics of Reed-Kellogg diagrams

I. Subject vs. predicate

To diagram a sentence, you have to divide it into its component parts, or constituents. The most important cut is between subject and predicate, which are separated with a vertical line. The predicate contains the verb marked for tense plus any objects or subjective or objective complements. The predicate always contains a verb phrase.

The minimal verb phrase is just a verb with tense marking (Pattern VI):

It rained.

That's ridiculous. (Pattern II) 

Alice considered the situation. (pattern VII) 

Alice sent Bob an email. (Pattern VIII) 

Alice considers Bob a fool. (Pattern X) 

II. Key elements and modifiers

The horizontal main line is for key structural elements: the subject, the verb, the direct object, the subjective complement, and the objective complement. Modifiers are placed under the element they modify:

Jack's fat cat purred loudly. 

Note, for example, that the head noun of a subject noun phrase and all of its modifiers go into the subject slot with the modifiers attached to the head noun:

The people who live in that small yellow house with the picket fence across the street from me raise emus. 

Similarly, verb modifiers (adverbials) are placed under the verb:

Hidden in the dense pile, the fat cat sat on the fluffy mat grinning smugly until I shooed her away. 

Note that the active and passive participles grinning and hidden have special l-shaped diagrams that distinguishes them from adjectives.

III. Diagrams and word order

Diagrams are graphic representations of sentence structure. They are not intended as linear representations of the order of words in sentences; instead they represent relationships between the elements of sentences and their modifiers.

For example, adverbs are often fairly movable within sentences, but a diagram places them under the verb to show their function, regardless of where they appear in the sentence:

Balefully, the monster eyed Beowulf.
or
The monster eyed Beowulf balefully.

Similarly, the adverbial prepositional phrase can appear in several different places in these sentences:

On Monday, I'm driving to Dallas to see the sights.
I'm driving to Dallas on Monday to see the sights.
I''m driving to Dallas to see the sights on Monday.
To see the sights, I'm driving to Dallas on Monday.

In this sentence, the clause that you find grammar frightening is appositive to (renames) the dummy subject it. The diagram sticks both into the subject slot at the left:

It is a shame that you find grammar scary. 

In sentences with expletive there, the expletive is not considered a part of the sentence's structure. Even though it usually comes first in the spoken or written sentence, it floats up over the main line in a diagram.

There is a unicorn in the garden. 

Subordinate clauses may precede main clauses in speaking or writing, but they go under the main clause in a diagram. An adverbial clause is always attached to the verb it modifies:

After the ants had ruined their picnic, Miranda and Sam went to MacDonald's.