Learn Dutch: Waar zijn de borden? - Where are the plates?

The singular word for plate is bord, and its diminutive is bordje (little plate). To make a diminutive plural, you just add an -s, never -en. So, 'Where are the little plates?' would be Waar zijn de bordjes?.

Why is the plural of bord formed with -en instead of -s?

In Dutch, most regular nouns get their plural by adding -en. You will see -s used sometimes, especially for words ending in certain single vowels, but -en is the standard plural ending for most words.

Why is the article de used here, when plate is usually het bord?

While it is indeed het bord in the singular, the plural of every noun in Dutch always uses the article de. So het bord becomes de borden.

Why do we use zijn in this sentence?

Zijn is the plural form of the verb to be (are). Since we are asking about multiple plates (de borden), the verb has to be plural. If it were just one plate, you would say Waar is het bord? (Where is the plate?).