säännöllisille
Säännöllisille is the allative plural form of the Finnish adjective säännöllinen, meaning regular. In Finnish, adjectives agree with the nouns they modify in number and case, and the allative case suffix -lle expresses direction or target, often translated as “to” or “for” in English when applied to noun phrases.
The form säännöllisille is used before plural nouns in the allative case. For example, säännöllisille ryhmille
Notes on usage: The allative plural form contrasts with other plural forms such as säännölliset (nominative)
In summary, säännöllisille is a grammatical form used to describe or refer to regular items in a