The letter Ð is a D with a line through it. The letter’s name is “eð” and its lowercase version is ð.
The letter has two possible pronunciations: it is normally quite soft like “then”, but at the end of sentences it sounds like Þ.

Soft ð

In normal situations, ð is similar to the English word “then”. Pronouncing it exactly like in English is fine.
There is however a tiny difference between “then” and ð: In “then” your tongue touches the bottom of your front teeth, while in ð the tip of your tongue only comes close to touching the back of your front teeth without actually touching it. Since the tongue doesn’t touch the front teeth, the sound is very soft.

So soft that it disappears

Since ð is so soft, it’s often not pronounced at all, particularly when speaking quickly:
  • ▶ Play Ég er að koma. [é er a koma]
  • ▶ Play Og hvað með það? [o kva me þa]
  • Það er alveg ágætt. [þa er alve ágætt]
In particular, you should take care to not pronounce the ð in the following words. Overpronouncing the ð sounds worse than not pronouncing it:
  • að – You should always pronounce it as just “a”
  • það – You should usually pronounce it as just “þa” (or “ða” in an unstressed position)

At the end of sentences

Like happens with many other sounds which use the voice, the voice disappears if the letter is at the end of a sentence.
At the end of sentences, ð has the same pronunciation as þ (similar to the English thick” or thunder”).
  • Ég hef farið í sund. [é hef farið í sund] – This is not at the end of a sentence, ð is just pronounced normally.
  • Ég hef farið. [é hef fariþ] – This is at the end of a sentence, ð is pronounced like þ.

No words begin with this the letter Ð. If you don’t have access to an Icelandic keyboard, you can substitute it with a “D”.