A final clause is a type of language construction that expresses a modification of the original statement. Some experts refer to the final clause as a dependent clause, as it is added to a fuller sentence. It is further defined as an adverbial clause that expresses a purpose, although clauses of this type don’t typically include adverbs. These types of constructions are also sometimes called clauses of purpose.
One type of final clause includes the word “that.” What comes after the word “that” is the final clause that shows a purpose for a preceding statement. For example, an English speaker or writer may say: “He traveled freely, so that he could see the sights of the country.” In an alternate form, more relevant to older, archaic forms of English, a similar sentence might go this way: “He traveled freely, that he should see the sights of the country.” Both of these could be considered sentences that include a final clause.
Another alternate construction for a final clause features a different word that changes the meaning of the clause to an opposite one. Where the above kinds of final clauses are called clauses of purpose, these opposite clauses could be called “opposite clauses of purpose,” in that they set up an outcome that is not desired. For instance, an English speaker or writer might say “He took the main road, lest he become lost.” This use of a final clause sets up the idea that the clause indicates the reason for the preceding statement based on something that the subject wants to avoid.
Other types of final clauses may exist in formal English. Some of these may include formal or legal language, such as the words, “wherefore” or “whereas.” Like many of the above examples, all of these uses of final clauses, or clauses of purpose, display somewhat antiquated versions of the English language. More common modern clauses of this type often use the words, “in order that,” to attach the clause to the greater sentence. For example, a modern English speaker might say: “Let’s get our work in on time, in order that we can benefit from a work-free weekend.” This still sounds relatively formal to many native English speakers, but delivers the clause of purpose without evidently antiquated language. A less formal equivalent would be, "so that."