Definition of "threefold"

"We recognise that electrifying more of the railway is likely to be necessary to deliver decarbonisation," it stated.There's clearly a growing momentum in that direction, but some significant hurdles have still to be overcome - not least the legacy of the three-fold increase in cost on the Great Western Electrification Programme, which has become the poster project for expensive wiring.

2020 May 20, Andrew Haines talks to Stefanie Foster, “Repurpose rail for the 2020s”, in Rail, page 33

In this way, we find some new pairs ( h 1 , 1 , h 2 , 1 ) {\displaystyle (h^{1,1},\;h^{2,1})} of Hodge numbers of Calabi-Yau threefolds.

2015, Xun Yu, “McKay correspondence and new Calabi-Yau threefolds”, in (Please provide the book title or journal name)‎