Learn Croatian: Svaki dan čitam na hrvatskom. Na taj način učim nove riječi. - Every day I read in Croatian. In that way I learn new words.

When talking about doing something in a specific language, like speaking, reading, or writing, Croatian uses the preposition na followed by the locative case. Using u would sound like you are talking about the grammatical rules or inner workings of the language itself.

In the phrase Na taj način, what case is being used?

It uses the accusative case. Although na often takes the locative case for static locations, here it forms a set phrase indicating a method or manner, which triggers the accusative. Because način is an inanimate masculine noun, its accusative form looks exactly like its nominative form.

Why is the feminine adjective ending used in nove riječi? Doesn't riječ look masculine?

The noun riječ is feminine, even though it ends in a consonant. It belongs to a special group of feminine nouns called the i-declension. Because it is the direct object here, it is in the accusative plural. The feminine accusative plural adjective ending is -e (hence nove), and the plural noun form is riječi.

Why is there no preposition before Svaki dan to mean 'every day'?