Learn Finnish: Kampaaja aikoo syventää sävyä, joskin en ole varma. - The hairdresser intends to deepen the shade, although I am not sure.

The root is the adjective syvä (deep). By adding the suffix -ntää (or -ntaa for back-vowel harmony), we create an active, transitive verb meaning "to make [adjective]." So, syventää means "to make deeper" or "to deepen." Because it is a transitive verb, it requires an object—someone is directly doing the action to something else.

Why is the object "sävyä" in the partitive case here?

Using the partitive sävyä (instead of the total object sävyn) shows that the change is relative or partial—the hairdresser is going to deepen the shade by "some amount." Verbs that adjust, alter, or change a state (like syventää or suurentaa) very often take a partitive object to show that the action doesn't have an absolute, finalized endpoint.

What is "joskin" and is it used differently than "vaikka"?

Joskin translates to "although" or "albeit" and is formed by combining jos (if) with the clitic -kin (also/even). While it means almost the same thing as vaikka (even though), joskin is slightly more formal and is perfectly suited for tacking on a reservation, concession, or afterthought at the end of a sentence.

Why is it "en ole varma" instead of "en ole varmaa" in a negative sentence?