Abstract Nouns with -mus and -mys
In Finnish, you can turn verbs into abstract nouns by adding the suffix -mus or -mys to the verb stem. These nouns usually represent the result of an action, a concept, or an official document.
Vowel harmony applies as always: use -mus if the word has back vowels (a, o, u) and -mys if it has front vowels (ä, ö, y) or only neutral vowels (e, i).
For example, the verb vaatia (to demand) becomes vaatimus (a demand). The verb nähdä (to see) becomes näkemys (a view or perspective).
Declining -mus Nouns
Words ending in -mus and -mys belong to a specific word type. When adding most case endings (like the genitive -n or inessive -ssa), the final -s changes to -kse-. The partitive case is the exception, where you add -ta or -tä directly to the basic form.
| Nominative (Basic) | Partitive (Basic + -ta/-tä) | Genitive (Stem + -n) |
|---|
| vaatimus | vaatimusta | vaatimuksen |
| näkemys | näkemystä | näkemyksen |
| rikkomus | rikkomusta | rikkomuksen |
Notice this stem change in action when these legal terms are used as grammatical objects or show possession:
Because these nouns are derived directly from verbs, learning them as pairs is highly effective. If you know the verb, you can usually guess the corresponding document or official act.
For instance, anoa (to petition) gives us anomus (a petition), and sitoutua (to commit) gives us sitoumus (a commitment).
Plurals
To form plural cases, the -kse- stem combines with the plural marker -i-, resulting in -ksi-. For example, when putting toivomus (request) into the illative plural (into the requests), it becomes toivomuksiin.