fourfold

• four-fold

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

• (Received Pronunciation) IPA^(key): /ˈfɔːfəʊld/
• (General American) IPA^(key): /ˈfɔɹ.foʊld/

  • Audio (General American):

    (file)

fourfold (not comparable)

1. Four times as great; quadruple.
2. Comprised of four individual members.
   • 1895, [Charles Hardy], The Aural System […]‎^[1], page 5:

     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.

• quadruple, quadruplicate

fourfold (not comparable)

1. By a factor of four.
   • 1611, The Holy Bible, […] (King James Version), London: […] Robert Barker, […], →OCLC, 2 Samuel 12:6:

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

• quadruply; see also Thesaurus:four times

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.

• quadruple, quadruplicate

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^[2]:

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