Learn Finnish: Kertoja on myös esiintyjä. - The narrator is also a performer.

It is derived from the verb kertoa (to tell). To make an actor noun meaning 'the person who does the action', you take the verb's strong stem. For a type 1 verb like kertoa, you remove the final -a to get the stem kerto-, and then add the suffix -ja to make kertoja (narrator or teller).

Why does esiintyjä end in -jä instead of -ja?

This is due to vowel harmony. The word comes from the verb esiintyä (to perform or appear). Because the vowels in the stem are front vowels (e, i, y), the suffix must also use a front vowel. Therefore, we use -jä instead of -ja.

Does the placement of myös matter in this sentence?

Yes, in Finnish, myös (also or too) is usually placed immediately before the word it emphasizes. By putting it right before esiintyjä, the sentence stresses that being a performer is the additional role the narrator has.

Can the -ja or -jä suffix refer to things other than people?

Usually, this suffix indicates a human actor, much like the '-er' suffix in the English words 'teacher' or 'performer'. However, it can sometimes refer to machines or tools that perform an action, though in this sentence both words clearly refer to a person.