It is monosyllabic and tiny. But it packs its own kind of punch and is infinitely versatile. It can be an adverb, an adjective, a conjunction, or a pronoun. It is just so.
As an adverb it must modify a verb, an adjective, or another adverb (the modified word is in italics): “I think so” (verb). “It is so colorful” (adjective). “He loves her so much” (adverb). A three-year old is asked “How big?” and responds, “So big”, as arms rise. Compare “she’s so beautiful” with “she’s very beautiful”; little so conveys a more emphatic image.
As an adjective, it must modify a noun (again, in italics). “The papers on his desk are always just so”. Or “The music of the Beach Boys is so-1968″. (So-1968 is an adjectival phrase modifying music). (If you’re one who keeps track of important cultural moments, you’ll want to know that so used in this sense is said to have originated in the 1992 movie, “Buffy the Vampire Slayer”.)
As a pronoun (where it refers to the same thing): “I expect to be away a week or so”. “The cost will be $15 or so”. “If you plan to file a claim, do so now!” (so refers to the infinitive phrase).
As a conjunction where it combines two independent clauses: “The boys missed their train, so that they’ll be late” (with the result that). “I don’t want to go, so I won’t” (therefore). “Be quiet, so that he can sleep” (in order that). (Note: The written conjunction so is said to require “that” after it, but the “that” is generally dropped when it is spoken.)
“So-called”, “so what!”, “so and so”, “so-long”, and “so-there!” are all phrases that are routinely a part of our vernacular and further illustrate so’s pervasiveness. It’s interesting to ponder the language without it.
Many who write about English grammar condemn the excessive use of so, especially as a conjunction where it is used in place of “therefore” or “thus” (“He hit the ball a mile, so he’ll be crossing the plate.’); but it’s as though they’re trying to quell an avalanche. It is here to stay, and how better to illustrate its versatility, than this: when Ronald Reagan was asked, “How was your first meeting with Desmond Tutu”, without missing a beat, he replied, “so-so”.
– Ken Butera