Learn Finnish: Tämän maan väkiluku on maailman kolmanneksi suurin. - This country's population is the world's third largest.

In Finnish, ranking superlatives like "second best" or "third largest" are built by putting the ordinal number into the translative case (-ksi), followed by the adjective in its normal superlative form. You can think of it as literally meaning "the largest, positioning into third place."

The basic word for "third" is kolmas. How exactly does it turn into kolmanneksi?

Ordinal numbers that end in -s (like kolmas, "third", or neljäs, "fourth") change their ending to -nne- when forming the stem for case endings. So kolmas becomes the stem kolmanne-, to which we attach the translative ending -ksi, giving us kolmanneksi.

Why is the word for "world" (maailma) in the genitive case (maailman)?

Finnish frequently uses the genitive case (the -n ending) to define the specific group or scope of a superlative, mirroring the English apostrophe-s. Maailman kolmanneksi suurin perfectly matches "the world's third largest." You could alternatively use the inessive case (maailmassa, meaning "in the world") placed after the adjective, but this genitive structure is extremely common and natural.

What is the literal breakdown of the compound word väkiluku (population)?