Names for sets of 2 to 10 items (doubleton, triplet, etc.) are derived with the ikkO suffix from the cardinal numerals, with some irregular changes in the base word: kaksikko, kolmikko, nelikko, viisikko, kuusikko, seitsikko, kahdeksikko, yhdeksikkö, kymmenikkö. Thus, for 7–9, these names coincide with the names of numbers.
Instead of kaksikko, the word pari (pair) is used in most contexts.
There is no commonly used word for a singelton in Finnish. (The word yksikkö exists, but it means “unit” or “singular” as a grammatical category.) The loanword singelton or singleton or its colloquial form singeli is used sometimes.
There are special derived nouns for sets of two or more people or animals born together (twins, triplets etc.): kaksoset, kolmoset, neloset, viitoset, kuutoset. The singular forms are kaksonen, kolmonen etc., so they coincide with the names of the numbers 3–6.