Phil Evans, a reader, inquires:

Do you answer readers' questions? If so, in the sentence, "It appears [that]

today will be hot." how do you explain when you must include "that" or when

it's OK to drop it?

I advise employees of a nonprofit child advocacy agency on writing and

frequently preach the value of short sentences. Perhaps as a consequence, I

see a lot of sentences that (?) I believe should include "that", but do not.

I believe the missing "that's" are considered function words and are

supposed to express a grammatical relationship. Even if that statement is

accurate, I have no idea of what it means. I am at a loss about how to

explain the correct usage to staff members who are experts in matters other

than writing.

You will understand my ignorance on this subject when I confess that (?) I

was a journalist most of my life including ten years at The Evening Sun.

We will speak no ill here of The Evening Sun.

Mr. Evans is correct that that is a function word. A function word, the Oxford English Grammar will tell you, is a class of words, such as conjunctions and prepositions, that indicate grammatical relationships between words or groups of words. Lexical words, such as nouns, indicate content rather than relationship.

That as a conjunction introduces dependent clauses, thus marking the relationship with the main clause.

It is often omitted, more commonly in speech than in edited texts, particularly when the main clause and dependent clause are both short. Think of the line from O Brother, Where Art Thou?, “We thought you was a toad.”

Such a construction is called a contact clause.

The Associated Press Stylebook offers useful advice. That can be omitted when a dependent clause follows the main clause immediately, as in the O Brother example.

It must be used when an adverb of time follows the main verb. They found out on Thursday that their ship had sailed.

Some verbs idiomatically require the use of that. They include advocate, assert, contend, declare, estimate, make clear, point out, propose and state. And it must be used before subordinate clauses that begin with after, although, because, before, in addition to, until and while. We are confident that until journalists start paying attention to the stylebook, there will be work for copy editors.

Journalists as a group tend to omit that, often to the effect of muddying meaning. The AP’s best advice is “When in doubt, include that. Omission can hurt. Inclusion never does.”

For my part, it is sobering to calculate how much time I have spent over the past 26 years inserting that into awkwardly phrased copy.