Learn Dutch: Zij vernietigen het harnas van de ridder.

While Dutch does have a possessive s, the van construction (literally "the armor of the knight") is overwhelmingly preferred in everyday Dutch for expressing possession with regular nouns. English relies much more heavily on the 's structure than Dutch does.

How do we know zij means "they" and not "she" in this sentence?

The verb form gives it away. Vernietigen is the plural form, so zij must mean "they". If it were "she", the verb would take the singular form: Zij vernietigt.

Where does the stress fall when pronouncing the verb vernietigen?

The stress falls on the second syllable: ver-NIE-ti-gen. This is because the inseparable prefix ver- is always unstressed in Dutch, just like the common prefixes be-, ge-, and ont-.

Is the word harnas only used for a literal suit of armor?

It primarily refers to a literal suit of armor, but just like in English, it can be used metaphorically. For instance, at this level you might encounter the common idiom in het harnas sterven, which literally means "to die in armor" but is used to mean dying while still actively working or performing your duties.