Learn Finnish: Väärennetty asiakirja taitaa olla passin kokoinen. - The forged document seems to be the size of a passport.

It combines the genitive of passi (passin) with the adjective kokoinen (sized) to mean "the size of a passport". While common pronouns and adjectives form single-word compounds with these endings (like samankokoinen), combinations with specific nouns like passi are written as two separate words.

What verb form is väärennetty?

It is the past passive participle (often called the TU-participle) of the verb väärentää (to forge). It acts as an adjective here, meaning "forged" or "falsified".

How does the verb taitaa work here?

Taitaa is an auxiliary verb that expresses probability, translating to "to probably do" or "to seem to". It requires the main verb to be in its basic dictionary form (first infinitive), which is why it is followed by olla (to be).

What are the parts of the word asiakirja?

It is a compound noun made from asia (matter, affair) and kirja (book). Together, they mean "document".