Questions & Answers about He istuvat tiiviisti hänen vieressään.
Why is there an -ään attached to the end of vieressä?
Vieressä is a postposition meaning "next to". In Finnish, when a postposition follows a personal pronoun in the genitive case—like hänen (his/her)—you must attach a matching possessive suffix to the postposition. Here, the 3rd-person suffix is formed by doubling the last vowel of vieressä and adding -n, resulting in vieressään.
Could I just say "He istuvat tiiviisti vieressään" and drop the word hänen?
No, you need to keep it here. While you can usually drop 1st and 2nd person pronouns (like minun or sinun) before a possessive suffix, you must keep 3rd person pronouns like hänen or heidän. You can only drop hänen if the subject of the sentence is doing the action to their own thing. Since "they" (he) are sitting next to "him" (hänen), you must keep the pronoun to show whose side they are on.
Is "vieressänsä" also correct instead of "vieressään"?
Yes! The 3rd-person possessive suffix has two valid forms: -nsa/-nsä or lengthening the final vowel and adding -n. Therefore, vieressänsä and vieressään are both grammatically correct and mean the exact same thing. However, vieressään is much more common and natural in modern Finnish.
How is the word tiiviisti (tightly) formed?