To understand the punctuation featured in Unit 3, you need to know the difference between a clause and a phrase. Remember that a clause has both a subject and a verb. A phrase, on the other hand, is a sequence of words that has some sort of meaning but does not have both a subject and a predicate. A phrase might have a noun or a pronoun, or it might have a verb, but it will not have a subject and a verb working together. A phrase might be short or long, but it does less grammatically than a clause.

Label each sentence of words cl (for clause) or p (for phrase):

1. ________ this man loved his child

2. ________ loving his child

3. ________ the water is deep

4. ________ in a certain depth of water

5. ________ closing the store soon

6. ________ devoted to the exploration of space

7. ________ if we expect to continue the quest

8. ________ expecting to continue the quest

The clauses are items 1, 3 and 7. The phrases are items 2, 4, 5, 6 and 8.

Introductory phrases

Read this sentence aloud:

Not leaving a thing to chance one cookbook says that Grandma’s “pinch” is really one-eighth of a teaspoon.

If you’re like most readers, this sentence cannot be read easily without a very short pause and a slight shift in vocal pitch after the word chance. Insert a comma after chance and read the sentence aloud again. It’s clearer with the comma, isn’t it?

Most writers would insert a comma after chance even if they know very little about the formal rules of punctuation. You might say it’s a commonsense comma. The reason it’s so helpful is that it separates what is called an introductory phrase from the independent clause that follows it. Go back to the sentence and draw a bracket over Not leaving a thing to chance; then write introductory phrase above the bracket. Finally, mark the main parts of the sentence’s independent clause.