Usage Note: Many critics and grammarians have insisted that so must be followed by that in formal writing when used to introduce a clause giving the reason for or purpose of an action: He stayed so that he could see the second feature. But since many respected writers use so for so that in formal writing, it seems best to consider the issue one of stylistic preference: The store stays open late so (or so that) people who work all day can buy groceries. ·Both so and so that are acceptably used to introduce clauses that state a result or consequence: The Bay Bridge was still closed, so (or so that) the drive from San Francisco to the Berkeley campus took an hour and a half. ·So is frequently used in informal speech to string together the elements of a narrative. In most cases, this practice should not be carried over into formal writing, where readers need connections to be made more explicit. ·Critics have sometimes objected to the use of so as an intensive meaning “to a great degree or extent,” as in We were so relieved to learn that the deadline had been extended. This usage is most common in informal contexts, perhaps because, unlike the neutral very, it presumes that the listener or reader will be sympathetic to the speaker's evaluation of the situation. Thus one would be more apt to say It was so unfair of them not to invite you than to say It was so fortunate that I didn't have to put up with your company. For just this reason, the construction may occasionally be used to good effect in more formal contexts to invite the reader to take the point of view of the speaker or subject: The request seemed to her to be quite reasonable; it was so unfair of the manager to refuse.
