aikuisiden

Aikuisiden is a form that may be encountered in Finnish texts, but it is not the standard genitive plural form of the noun aikui nen. The base word aik uinen means an adult, and in standard Finnish the genitive plural is aikuisten. The nominative plural is aikuiset, and the partitive plural is aikuisia.

In Finnish, nouns that end in -nen are typically declined with a genitive plural ending -isten (as in aikuisten). This contrasts with the form aikuisien, which reflects the common genitive plural for many speakers and writers in everyday language. Standard reference usage, however, consistently shows aikuisten as the correct genitive plural when referring to “of adults” or “the adults’ …”.

Correct usage examples include:

- aikuisten oikeudet (the rights of adults)

- aikuisten ryhmä (a group of adults)

- aikuisten ja lasten harrastukset (the hobbies of adults and children)

The form aikuisiden is not accepted in formal or widely edited Finnish, and readers should replace it with aikuisten in formal writing. If encountered, aikuisiden may reflect a misspelling, regional variation, or a copy-editing mistake rather than standard grammar.

See also: aikuiset, aikuinen (the base noun), Finnish grammar, genitive plural.