"That as a conjunction" introduces dependent clauses that provide essential information, often replacing a noun or clause. It functions as a subordinating conjunction, connecting ideas within a sentence while marking a shift from independent to dependent thought.
Unlike coordinating conjunctions such as "and," "but," or "or," which join equal parts of speech, "that" introduces a clause that cannot stand alone. It signals that the following clause depends on the main clause for meaning. This role differs from "that" used as a relative pronoun (e.g., "the book that I read") or as a demonstrative pronoun (e.g., "that is mine").
When used as a conjunction, "that" typically follows a verb of saying, thinking, or believing. For example: "She said that she was tired." Here, "that" introduces the reported clause, making it subordinate to the main clause. The conjunction does not carry grammatical weight on its own-it serves purely structural function.
The conjunction "that" establishes a relationship between two clauses by marking the second as dependent. It does not express contrast, addition, or condition-those roles belong to other conjunctions like "but," "and," or "if."
Consider this sentence: "I believe that the test will be difficult." The main clause is "I believe," and the dependent clause is "the test will be difficult." Without "that," the sentence would still be grammatically correct: "I believe the test will be difficult." But including "that" clarifies the structure, especially in formal or written English.
Not all verbs require "that" as a conjunction. Verbs like "know," "think," "say," and "believe" often take "that" to introduce a clause. However, omitting "that" is common in informal speech and writing. For example: "He told me he left early" is acceptable in casual contexts, though "He told me that he left early" is preferred in formal writing.
While "that" as a conjunction appears in only one form, its usage varies based on context. It may appear in direct or indirect speech, embedded clauses, or conditional constructions.
| Use Case | Example | Function |
|---|---|---|
| Reporting speech | She said that she was late. | Introduces reported clause |
| Expressing belief | I think that we should leave now. | Subordinates opinion |
| Stating facts | They proved that the system was flawed. | Introduces evidence |
Some writers mistakenly treat "that" as a connector between independent clauses. That error occurs when someone writes: "The meeting ended, that was unexpected." This is incorrect because "that" cannot join two independent clauses. A correct version uses a coordinating conjunction: "The meeting ended, but that was unexpected." Or better yet: "The meeting ended unexpectedly."
A frequent mistake is confusing "that" as a conjunction with "which" or "who" in relative clauses. For example: "The car that I bought is red." Here, "that" acts as a relative pronoun, not a conjunction. It refers to "car" and introduces a defining clause. In contrast, "that" as a conjunction introduces a clause that depends on the main clause, not on a noun.
Another confusion arises when people assume "that" must always be included. While it's standard in formal writing, omission is acceptable in spoken English and creative writing. For example: "I saw you were upset" is grammatically sound and widely used. However, in academic or technical writing, including "that" improves clarity and precision.
Non-obvious fact: "That" as a conjunction can be omitted only when the dependent clause begins with a subject, not a verb. In "She said she was tired," "that" is optional. But in "She said that she had seen it," removing "that" creates ambiguity-readers might misinterpret the clause structure. The presence of "that" prevents misreading in complex sentences.
Consider this sentence from a news report: "The mayor announced that the city would implement new traffic regulations." The main clause is "The mayor announced," and the dependent clause is "the city would implement new traffic regulations." The conjunction "that" marks the dependency.
If "that" were removed, the sentence becomes: "The mayor announced the city would implement new traffic regulations." While still grammatical, it risks sounding abrupt or unclear in formal contexts. The original version maintains a clear hierarchy of ideas.
Another example: "Scientists confirmed that climate change is accelerating." Here, "that" introduces the claim being confirmed. Omitting it results in: "Scientists confirmed climate change is accelerating." The meaning remains intact, but the omission reduces syntactic precision-especially important in scientific or legal documents.
Confusion often arises between "that" as a conjunction and "that" as a demonstrative pronoun. The latter refers to a specific noun: "That is my favorite painting." In contrast, "that" as a conjunction introduces a clause: "I know that you're right."
Also, "that" should not be used with "whether" or "if" in conditional statements. For example: "I don't know that whether it will rain" is redundant. Correct versions: "I don't know whether it will rain" or "I don't know if it will rain." Using "that" with "whether" or "if" creates a double conjunction error.
Understanding "that as a conjunction" enhances precision in writing. It is not interchangeable with coordinating conjunctions, nor is it optional in all contexts. Its role is structural-not expressive-and it shapes how readers interpret relationships between ideas.