Questions & Answers about Wir lieben die Terrasse, die sehr groß ist.
Why is the second die used here instead of welche or das?
The second die is a relative pronoun meaning 'which' or 'that'. It refers back to die Terrasse. Because Terrasse is a feminine noun and acts as the subject of the relative clause ('which is very big'), we use the feminine nominative relative pronoun die. While welche is also grammatically correct, die is much more natural in everyday German.
Why does ist come at the very end of the sentence?
The phrase die sehr groß ist is a relative clause, which is a type of subordinate clause. In German, subordinate clauses always kick the conjugated verb (in this case, ist) to the very end of the clause.
How could we apply this lesson's topic to say: 'We love not only the terrace, but also the garden'?
You would say: Wir lieben nicht nur die Terrasse, die sehr groß ist, sondern auch den Garten. The two-part conjunction nicht nur ... sondern auch (not only ... but also) frames the things being paired. Notice that den Garten takes the accusative case, just like die Terrasse, because both are direct objects of the verb lieben.
Is the comma before the relative clause mandatory?