fourfold

From Middle English fourfold, fourefold, from Old English fēowerfeald. Equivalent to four +‎ -fold. Cognate with Dutch viervoud, Gothic 𐍆𐌹𐌳𐌿𐍂𐍆𐌰𐌻𐌸𐍃 (fidurfalþs).

fourfold (not comparable)

1. four times as great; quadruple

fourfold (not comparable)

1. by a factor of four
   • Bible, 2. Sam. xii. 6

     He shall restore the lamb fourfold.

fourfold (third-person singular simple present fourfolds, present participle fourfolding, simple past and past participle fourfolded)

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

fourfold (plural fourfolds)

1. (mathematics) An algebraic variety of degree 4.
   • 2015, Brent Pym, “Elliptic singularities on log symplectic manifolds and Feigin--Odesskii Poisson brackets”, in arXiv‎:

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