Viidentoista vuoden kuluttua esikoinen on aikuinen.
In fifteen years, the firstborn will be an adult.
Breakdown of Viidentoista vuoden kuluttua esikoinen on aikuinen.
olla
to be
viisitoista
fifteen
vuosi
year
aikuinen
the adult
Questions & Answers about Viidentoista vuoden kuluttua esikoinen on aikuinen.
Why does viisitoista become viidentoista here instead of inflecting the whole word?
When you put a teen number (11-19) into a new case, only the first part changes, and the -toista ending stays exactly the same. The genitive of viisi is viiden, so the word becomes viidentoista.
Why is viidentoista vuoden in the genitive case?
The postposition kuluttua, which means "in" or "after" a period of time, always requires the preceding words to be in the genitive case. This is a key difference from sitten (ago), which uses the nominative or partitive.
Could I say viidentoista vuoden päästä instead?
Yes! Kuluttua and päästä both mean exactly the same thing here ("in" or "after" an amount of time) and both require the genitive case. You can use them interchangeably.
The translation says "will be," but the sentence uses the present tense on. How do we know it is in the future?
Finnish does not have a separate future tense. You just use the present tense verb (on), and the time phrase viidentoista vuoden kuluttua makes it completely clear that this is happening in the future.