fourfold

adj

1. (not-comparable)Four times as great; quadruple.
2. (not-comparable)Comprised of four individual members.

   “Most pupils have a fourfold object in studying a language; they wish to be able to read and write, to speak and to understand it.”

adv

1. (not-comparable)By a factor of four.

   “And he shall restore the Lambe fourefold, because he did this thing, and because he had no pittie.”

verb

1. To increase to four times as much; to multiply by four.

noun

1. An algebraic variety of degree 4.

   “Our main application is to the classification of Poisson brackets on Fano fourfolds.”