Breakdown of Sinun kannattaa vaihtaa multa kerran vuodessa.
sinä
you
vuosi
year
vaihtaa
to exchange / to change (switch)
kannattaa
to be profitable / to be worth it
Questions & Answers about Sinun kannattaa vaihtaa multa kerran vuodessa.
Why do we use vuodessa here?
To express how often something happens during a specific time period, Finnish uses the inessive case (-ssa/-ssä) for the time period. So, kerran vuodessa literally means 'one time in a year'. This is the standard way to say 'per year' or 'a year' in frequency expressions.
Why is the object multa (soil) in the basic nominative form and not mullan or multaa?
This is because of the verb kannattaa (to be worthwhile / should). With verbs expressing necessity or obligation (like täytyy, pitää, and kannattaa), a whole object takes the basic nominative form instead of the usual -n ending. If this were a normal sentence like 'You change the soil' (Sinä vaihdat mullan), the object would take the -n ending.
Why is the subject sinun in the genitive case instead of sinä?
The verb kannattaa requires its logical subject to be in the genitive case (sinun). The verb itself always stays in the third-person singular (kannattaa), no matter who is doing the action. It translates roughly as 'It is worthwhile of you to change...'.
What form is the word kerran?