Compounds with a cardinal numeral as the first part and kertainen as the second part mean something that is repeated the given number of times or has something repeated that many times. For example, kolminkertainen means “triple, treble, threefold, triplex, three-ply”. These words have normal adverb derivations, e.g. kolminkertaisesti (triply).
The form of the numeral in these compounds varies:
When the number is written with digits in such a context, it is customarily written without indicating inflection of the number, e.g. 3-kertainen, even though this in principle breaks the rules of the language: kolmin should be written 3:in.