Learn Finnish: Teini ansaitsee viikkorahaa tekemällä kotitöitä, sikäli kuin hän on ahkera. - The teen earns a weekly allowance by doing chores, insofar as he is diligent.

While both express a condition, sikäli kuin translates to "insofar as" or "provided that." It emphasizes the extent to which the condition is met. It tells us that the teen earning the allowance is strictly limited by the degree of their diligence, making it slightly more formal and restrictive than a plain jos.

Why does the sentence use tekemällä to say "by doing"?

tekemällä is the adessive case (-llä) of the third infinitive (often called the MA-infinitive). Adding the adessive ending to this infinitive form is the standard Finnish way to express the means or method of an action, translating perfectly to "by [verb]-ing" in English.

Why are both viikkorahaa and kotitöitä in the partitive case?

Both are objects representing undefined amounts. viikkorahaa (partitive singular) is treated as an uncountable mass noun here. kotitöitä (partitive plural) refers to an unspecified number of chores. If the teen had to do all the specific chores on a finite list to get paid, you would use the accusative plural kotityöt.

Does the verb ansaita only mean "to earn" in a financial sense?