Genitive Compound Adjectives
When describing physical traits like appearance, size, or age in Finnish, use the adjectives -näköinen (looking like), -kokoinen (the size of), and -ikäinen (the age of).
These words function as the second half of a descriptive pair. The first word—which provides the specific description—must be in the genitive case (ending in -n).
Asking Questions: Minkä...?
To ask about someone's age or the size of an object, use the genitive form of the question word mikä (minkä).
Using Nouns as Modifiers
You can use a noun or noun phrase in the genitive case to compare a subject's size, age, or appearance to a specific object or person. For example, passi (passport) becomes passin.
Describing Traits with Adjectives
To describe an appearance directly (e.g., "strange-looking" or "real-looking"), pair a descriptive adjective in the genitive case with -näköinen.
Declining the Compound Structure
Because -näköinen, -kokoinen, and -ikäinen are adjectives, they must agree in case and number with the noun they describe.
Here is the vital rule for these structures: the first word is locked into the genitive case, but the second word declines to match the noun.
Notice in the examples below how the first word (oudon, vaarallisen) remains in the genitive case, while the second word declines into the adessive case (-llä) or the accusative/genitive case (-n) to match the suspect (epäilty).