Learn Finnish: Arvoisa ryhmä, seuratkaa opettajaa! - Esteemed group, follow the teacher!

Seurata (to follow) is a type 4 verb. To make the plural or formal command, you take the infinitive seurata, drop the final vowel to get the stem seurat-, and add the plural imperative ending -kaa. This gives us seuratkaa.

The word ryhmä (group) is singular. Why do we use the plural command seuratkaa instead of the singular seuraa?

Even though ryhmä is grammatically singular, it refers to a collection of multiple people. Since the speaker is addressing multiple people at once, they must use the plural imperative ending -kaa.

Why does opettajaa have the partitive ending -a here?

The verb seurata (to follow) is a partitive verb. This means its object must always be in the partitive case. In Finnish, following someone is treated as an ongoing process rather than a completed action, so you use opettajaa.

Is arvoisa a common way to say "dear" in Finnish?

Arvoisa is quite formal and translates closer to "esteemed" or "honorable." It is mostly used for speeches, official announcements, or very polite addresses. For an everyday letter to a friend, you would use rakas or hyvä instead.