fourfold

adj, adv 1 four times as much or as many 四倍（的）: The population in this area has increased fourfold. 该地区的人口已增加到四倍. 2 having four parts 有四部分（的）.

foundation course, foundation-stone, foundations, founder, founder-member, founding father, foundling, foundry, fount, fountain, fountain-head, fountain-pen, four, four-, four-in-hand, four-letter word, four-ply, four-poster, four-square, four-wheel drive, foursome, fourteen, fourteenth, fourth, fowl, fowl pest, fox, fox-hunting, fox-terrier, foxglove, foxhole, foxhound, foxtrot, foxy, foyer, FPA, Fr, fracas, fraction, fractional,