Learn Finnish: Tämä omena on oranssi.

No! In Finnish, oranssi only refers to the color. If you want to talk about the fruit orange, you must use the word appelsiini. So, you would never eat an oranssi, but you could eat an oranssi appelsiini (an orange orange)!

Why does the word oranssi have a double S?

Oranssi is a loanword borrowed from other languages. Finnish often adapts foreign words to fit its own spelling and pronunciation rules, which frequently involves adding double consonants. Remember to hold that S sound slightly longer when you say it out loud!

Why doesn't the word tämä change its ending here?

Tämä (this) is in its basic dictionary form, just like omena. In Finnish, pointer words like tämä always have to match the grammatical form of the noun they are attached to. Since the apple is the main subject of the sentence and in its basic form, tämä stays basic too.

The words omena and oranssi end in different vowels. Do adjectives need to match the noun's ending perfectly?

No, they do not need to rhyme or have the exact same letters. They only need to match in their grammatical state. Both omena and oranssi are singular and in their basic dictionary forms here, which is all the matching they need to do!