Learn Hardcore Finnish: Olen oppinut uuden säännön tänään.

In Finnish, verb endings already show person and number. The “-en” in olen marks first person singular, so minä (“I”) is redundant and usually dropped. You could say Minä olen oppinut… for emphasis, but it’s not required.

How is the perfect tense formed in Finnish, as seen in olen oppinut?

Finnish forms the perfect with the present tense of olla (“to be”) plus the past participle of the main verb. Here it is:

olla (1 sg. present) → olen
oppia (past participle) → oppinut
Together olen oppinut literally means “I have learned.”

Should olen oppinut always be translated as “I have learned,” or can it also mean “I learned”?

Although it’s grammatically the present perfect, Finnish often uses the perfect where English would use the simple past. You can translate Olen oppinut uuden säännön tänään as either “I have learned a new rule today” or “I learned a new rule today” without changing the basic meaning.

Why is uuden säännön in the genitive case? When would you use the partitive instead?

A direct object that is complete and definite takes the genitive (sometimes called the accusative) in Finnish, marking a finished, one-off action.

uusi sääntö (nom.) → uuden säännön (gen.)
Use the partitive (e.g. uuttA sääntöä) if the action is partial, ongoing, indefinite, or you’re referring to an unspecified amount.

How do you decline uusi sääntö into uuden säännön?

Both adjective and noun are declined:

uusi (nominative) → uuden (genitive)
sääntö (nominative) → säännön (genitive)
Note the stem changes (“uusi → uuden” and “sääntö → säännön”).

Can you move tänään elsewhere in the sentence, and does it change the meaning?

Finnish word order is quite flexible. You can place tänään at the start, in the middle, or at the end:

Tänään olen oppinut uuden säännön.
Olen tänään oppinut uuden säännön.
Olen oppinut tänään uuden säännön.
The core meaning (“I learned a new rule today”) remains the same; shifting tänään just changes which part of the sentence you emphasize.