Learn Italian: I centrotavola di vetro sono eleganti. - The glass centerpieces are elegant.

Centrotavola is an invariable compound noun, meaning it stays exactly the same in the plural. It is made of two nouns of different genders: centro (masculine) and tavola (feminine). When a compound noun is formed this way, you usually only change the article (il to i) to make it plural, rather than changing the word's ending.

Since centrotavola ends in -a, why does it take the masculine plural article i?

The gender of a compound word made of two nouns is usually determined by the first noun, which gives the core meaning to the word. Because centro is masculine, the whole word centrotavola is masculine. Even though it ends in the feminine -a from tavola, we use the masculine articles il (singular) and i (plural).

Why do we use di vetro instead of an adjective for "glass"?

In Italian, nouns for materials aren't used directly as adjectives like they are in English. Instead, you use the preposition di (of) followed by the noun for the material. So, "glass centerpieces" literally becomes "centerpieces of glass" (i centrotavola di vetro).

How does eleganti match centrotavola if they have different endings?