Järjestetyissä
Järjestetyissä is the inessive plural form of the Finnish past participle järjestetty, derived from the verb järjestää, meaning to organize or to arrange. Järjestetty functions as an adjective meaning "organized" or "arranged." As a participial adjective, järjestetty describes nouns and agrees with them in number and case. Järjestetyissä is the plural inessive form, used to say “in the organized [ones/things].” In Finnish, the inessive plural suffix is -issa/-issä, chosen according to vowel harmony; with the stem järjestetty the form becomes järjestetyissä.
In practice, järjestetyissä appears in phrases describing plural nouns that are located or assumed to be organized.
Note that järjestetyissä is a grammatical inflection rather than a separate concept. It expresses organization as
See also: Finnish grammar, past participles, inessive case, suffixes -ssa/-issä.