Learn Icelandic: Hér er stór rétthyrningur.

While many masculine adjectives in the nominative case end in -ur (like góður or kaldur), stór is an exception. Because the root word already ends in an -r, it drops the expected -ur ending. The masculine singular nominative form is just stór.

How is the word rétthyrningur constructed?

It is a compound word made of rétt- (right or straight) and -hyrningur (a shape with corners). The suffix comes from the word horn (corner or angle). Literally, it translates to "right-angled shape." You will see -hyrningur in other shapes too, like þríhyrningur (triangle).

Could I use hérna instead of hér in this sentence?

Yes, you can. Both mean "here" and are largely interchangeable. However, hér is slightly more formal and precise, pointing to an exact spot. Hérna is more conversational and is also commonly used as a filler word in spoken Icelandic, much like "umm" or "well" in English.