Questions & Answers about Minä kirjoitan viestin heti.
Why is the object viestin instead of viesti?
Viestin has the -n ending because it is a total object. This means the action will be fully completed: you are going to finish writing the entire message. In affirmative sentences, a singular completed object gets this -n ending (which looks exactly like the genitive ending).
The translation says "I will write", but isn't kirjoitan in the present tense?
Yes, kirjoitan is the present tense. Finnish doesn't have a separate future tense word like "will". Instead, using the present tense verb combined with a total object (like viestin) shows that an action will be completed in the future.
Where does the second "t" go in kirjoitan?
The dictionary form of the verb is kirjoittaa. When you add the personal ending -n for "I", the double tt weakens to a single t due to consonant gradation (a pattern where consonants soften when a syllable gets closed by a consonant). So, kirjoittaa becomes kirjoitan.
Could I leave out Minä and just say "Kirjoitan viestin heti"?
Absolutely! Because the verb ending -n in kirjoitan already tells us that "I" am doing the action, the pronoun minä is optional. Including it just adds a little bit of emphasis.