Three times as much, or three times as many. If prices rise threefold, they become three times what they were. It is a formal word — you meet it in news reports, business writing, and science papers, and almost never in casual conversation, where people just say 'three times' or 'tripled'. It works two ways. As an adverb after a verb: 'Sales increased threefold last year.' As an adjective before a noun: 'a threefold increase in cases'. Both are common; the adjective form is a little more frequent in writing. There is a second meaning worth knowing: 'having three parts'. 'The problem is threefold' means the problem has three separate sides to it, and the speaker is about to list them. This use has nothing to do with multiplying — it is closer to 'in three parts'. You hear it in presentations and essays: 'Our aim is threefold: to teach, to test, and to encourage.' The -fold ending is productive: twofold, fourfold, tenfold, a hundredfold. Of these, tenfold is the one you will actually meet most often.

三倍（地）；也指「有三個層面／分三方面」。新聞和報告裡常見，日常口語通常直接說「變成三倍」。