Learn Finnish: Nämäkin sukat ovat yksivärisiä. - These socks too are solid-colored.

It acts as the subject complement because it describes the subject (sukat) using the verb ovat (are). When the subject is plural, an adjective describing it after the verb to be is almost always in the partitive plural.

Why does sukat use the nominative plural instead of matching the partitive plural?

In this sentence structure, the subject (sukat) takes the basic nominative plural case. The adjective only takes the partitive plural because it stands alone after the verb as a complement. If the adjective was placed directly in front of the noun instead, they would match cases, like in the phrase nämä yksiväriset sukat (these solid-colored socks).

How is the word yksivärisiä formed?

The base adjective is yksivärinen (solid-colored), which combines yksi (one) and väri (color). For adjectives ending in -nen, you form the partitive plural by replacing the -nen ending with -siä (or -sia, depending on vowel harmony).

What does the -kin ending on nämäkin do?

The suffix -kin means also or too. It attaches directly to the word you want to emphasize. By attaching to nämä (these), it specifically highlights the pronoun, meaning these too or even these.