Learn Icelandic: Maðurinn þekkir þær ekki. - The man does not know them f..

In Icelandic, the word for "them" changes depending on the gender of the group you are talking about. Þær is the accusative feminine plural, meaning the man doesn't know a specific group of females. If he didn't know a group of men, it would be þá, and for a mixed-gender group, it would be þau.

I've learned that "to know" is vita. Why use þekkir here?

Icelandic has two different verbs for "to know". You use þekkja (here as þekkir) when you mean being acquainted with a person, place, or thing. You use vita when you know a fact or a piece of information. Since the man doesn't know a group of people, we use þekkir.

Why does ekki (not) come at the very end instead of right after the verb?

When the object of your sentence is a pronoun like þær (them), the negative word ekki usually comes after the pronoun. If the object were a regular noun instead, ekki would come before it. For example, if it were "The man does not know the women", it would be Maðurinn þekkir ekki konurnar.

How does maðurinn mean "the man"?

In Icelandic, "the" isn't a separate word that goes in front. Instead, it gets attached to the end of the noun. The base word for "man" is maður. By adding the definite article ending -inn, it becomes maðurinn (the man).