All about “that”
“That” is a lazy word, too often used when the writer doesn’t take the care to form (or revise) a sentence using proper grammatical structure. “That” is properly used to introduce a restrictive clause, meaning a clause that complements the topic of the sentence. It is not properly used to bridge between between subject and predicate.
Improper use of that: “He explained that the immersion of an ice cube in warm water….” Simply remove “that” and the sentence is just as clear. Or even better, “He explained how immersing an ice cube in warm water…,” which eliminates another lazy usage, “the ___ of ___.”
Proper use of that in a restrictive clause: “He looked for the ice cube that he had left on the counter, but it wasn’t there.” As you can see, the restrictive clause, “that he had left on the counter”, can be removed entirely without loss of meaning.
Another misuse of “that” is when it is used to refer to a person, in which case “who” is the proper pronoun. “That” refers to an object. Some may quibble with this, but we still believe books should employ the best diction. For the quibblers, read Grammar Girl’s post:
Run a search on the next manuscript you edit to check for “that” usage. I rigorously and constantly edit myself to remove “that” from my writing.
Quotes on Writing: “Pronoun, adjective, adverb, conjunction, that is easily overused, but it’s best to use that only when not doing so disturbs the meaning or euphony of your words.” — Robert Hartwell Fiske, Editor and Publisher, The Vocabula Review.