Three times as great or many:
— A threefold increase.

synoniemen: three-fold, treble, triple.

Roget 93: treble, triple; tern, ternary; triplicate, threefold, trilogistic^†; third; trinal^†, trine.   

Having more than one decidedly dissimilar aspects or qualities.

synoniemen: double, dual, three-fold, treble, two-fold, twofold.

Pools: dychotomiczny, dwoisty, dualistyczny

By a factor of three:
— Our rent increased threefold in the past five years.

synoniem: three times.