The coördinating conjunction need not actually appear in the sentence. Its omission is then indicated by the punctuation: [John wished to play Indian; Richard preferred another game].
+81. Subordinate Conjunctions and Complex Sentences.+—A subordinate conjunction is used to join a subordinate clause to a principal clause, thus forming a complex sentence. The test to be applied to a clause in order to ascertain whether it is a subordinate clause, is this: if any group of words in a sentence, containing a subject and predicate, fulfills the office of some single part of speech, it is a subordinate clause. In the sentence, "I went because I knew that I must," the clause, "because I knew that I must" states the reason for the action named in the main clause. It, therefore, stands in adverbial relation to the verb "went." "That I must" is the object of "knew." It, therefore, stands in a substantive relation to the verb.
Subordinate clauses are often introduced by subordinate conjunctions (sometimes by relative pronouns or adverbs); but, whenever such a clause appears in a sentence, otherwise simple, the sentence is complex. If it appears in a sentence otherwise compound, the sentence is compound-complex.
The different types of subordinate clauses will be discussed later.
SENTENCE STRUCTURE
+82. Phrases.+—Phrases are classified both as to structure and use.
From the standpoint of structure, a phrase is classified from its introductory word or words, as:—
1. Prepositional: [They were in the temple].
2. Infinitive: [He tried to make us hear].
3. Participial: [Having finished my letter].