as . . . as

Also, so . . . as. Used with an adjective or adverb to show similarity or equality of one thing with another. The as . . . as construction appears in numerous similes, including the idioms as rich as Croesus, as big as life, as good as done. (In this book, when such idioms occur without the first as, they can be found under the adjective or adverb, rich as . . .; big as . . .; good as . . .; etc.; those that do not, like as far as, as long as, as well as, are found at as below.) The construction so . . . as is often preferred in negative statements like I couldn't sleep, not so much as a wink, a usage dating from the 1200s. Also see as far as.