Proficiency and skill rections (-ssa / -misessa)

In English, we say someone is "good at" or "terrible at" something. In Finnish, adjectives describing skill or proficiency—such as hyvä (good), etevä (capable), surkea (terrible), or keskinkertainen (mediocre)—require the inessive case (-ssa / -ssä).

Skills with Nouns

When the area of competence is a noun, simply attach the inessive ending.

We are looking for an expert who is capable at problem-solving.
Etsimme osaajaa, joka on etevä ongelmanratkaisussa.
I am terrible at recruitment, which is a big problem.
Olen surkea rekrytoinnissa, mikä on suuri ongelma.

Skills with Verbs (-misessa)

To express skill at doing an action, turn the verb into a noun using the 4th infinitive (-minen). In the inessive case, this ending becomes -misessa or -misessä.

For example, organisoida (to organize) becomes organisoiminen (organizing). Adding the inessive ending makes it organisoimisessa.

On the one hand he is only mediocre at organizing, but on the other hand capable at leadership.
Toisaalta hän on vain keskinkertainen organisoimisessa, mutta toisaalta etevä johtamisessa.
We assess suitability, because the manager must be capable at listening.
Arvioimme soveltuvuutta, koska johtajan täytyy olla etevä kuuntelemisessa.
The manager whom I interviewed was mediocre at speaking.
Johtaja, jota haastattelin, oli keskinkertainen puhumisessa.