þ and ð: The Two 'th' Sounds | Icelandic Grammar

These are the two letters English speakers find most exotic in Icelandic — and the good news is you can already pronounce both of them perfectly. You use them every day. þ (thorn) is the th in thin, think, thumb. ð (eth) is the th in this, that, mother. English writes both with the same two letters, "th," and never makes you stop and choose. Icelandic gives each sound its own letter and forces the distinction out into the open. So your job is not to learn two new sounds — it is to learn which sound goes with which letter, and to notice a difference your native language has always hidden from you.

The two sounds: it's all about voicing

Put your fingers on your throat and say the th of thin. No buzz — your vocal cords are not vibrating. That is voiceless, and that is þ.

Now say the th of this. You feel a buzz — your vocal cords are vibrating. That is voiced, and that is ð.

The mouth position is identical for both: tongue tip just touching the back of the upper teeth, air flowing through. The only difference is whether the vocal cords are switched on. That is the whole contrast.

Letter	Name	IPA	Voicing	English equivalent
þ	thorn (þorn)	/θ/	voiceless	"th" in thin
ð	eth (eð)	/ð/	voiced	"th" in this

þú

you — voiceless þ, like 'thoo' but with the th of 'thin'

það

it / that — begins with voiceless þ; one of the most common words in the language

maður

man / person — the ð is voiced, like the th in 'mother'

The iron distribution rule: where each letter can stand

This is the rule that makes þ and ð easy to keep straight, because their positions almost never overlap:

þ occurs only at the START of a word or morpheme. það, þú, þrír, þakka. It is never word-final.
ð occurs only word-medially and word-finally. maður, móðir, góður, með, við. It is never word-initial.

So if a "th" sound starts a word, it is þ. If it sits in the middle or at the end of a word, it is ð. They are in near-complementary distribution — the position tells you which letter, and which letter tells you the voicing. (The orthographic details of why this distribution holds belong to The Icelandic Alphabet; here you only need the core fact.)

þrír

three — initial þ, voiceless: 'threer' with the th of 'thin'

þakka þér fyrir

thank you — two initial þ in a row, both voiceless ('thank-a thyer fee-rir')

góður

good — medial ð, voiced: 'GOH-thur' with the th of 'this'

með

with — final ð, voiced; very common little word

við

we / by, at — final ð, voiced

💡

Position is your cheat code: a "th" at the start of a word is always voiceless þ; a "th" in the middle or end is always voiced ð. Once this sinks in you rarely have to think about which sound to make — the spelling decides for you.

A near-pair to feel the difference

Hold a single word with ð against a single word with þ and switch your throat-buzz on and off:

norður

north — medial ð, VOICED ('NOR-thur', th of 'this')

þú

you — initial þ, VOICELESS ('thoo', th of 'thin')

Now a sentence that uses both letters so you practise flipping voicing inside one breath:

Þú ferð norður með móður þinni.

You're going north with your mother. — initial þ (voiceless) in Þú/þinni, medial/final ð (voiced) in ferð, norður, móður.

Why this is genuinely hard for English speakers (and why it isn't)

Here is the distinguishing insight. In English, the voiced/voiceless th split is allophonically conditioned — your brain chooses between them automatically based on the word, and you have never once had to think about it. Compare thigh (voiceless) and thy (voiced): same spelling, different sound, and you produce the right one without effort. Because the choice is automatic and unspelled, most native English speakers are not even consciously aware there are two th sounds at all.

Icelandic makes that hidden, automatic choice phonemic — meaningful — and spells it. So the difficulty is not articulatory (you already make both sounds flawlessly); it is one of awareness. You have to bring a distinction your native language kept on autopilot up into conscious control. Once you can hear the voicing — feel the throat buzz or its absence — the rest follows from the distribution rule.

þing

parliament / assembly — initial þ, voiceless; compare the English word 'thing', which also has voiceless th

veður

weather — medial ð, voiced; compare English 'weather', also voiced th

Common Mistakes

❌ það — pronounced with a hard 't', as 'tað'

Incorrect — þ is a 'th' (the soft fricative of 'thin'), never a hard t. Substituting t is the most common slip.

✅ það — voiceless 'th' of 'thin'

it / that

❌ þú — pronounced with the voiced 'th' of 'this'

Incorrect — initial þ is voiceless. Voicing it turns it into the wrong sound (and would be spelled ð, which can't start a word).

✅ þú — voiceless 'th' of 'thin'

you

❌ maður — pronounced with the voiceless 'th' of 'thin'

Incorrect — medial ð is voiced ('th' of 'this'); devoicing it into a þ-sound is the classic reverse error.

✅ maður — voiced 'th' of 'this'

man / person

❌ Writing *þaður or *maþur, mixing up the letters

Incorrect — þ can never stand medially/finally and ð can never start a word; the positions are fixed.

✅ maður (medial ð), það (initial þ)

man; it/that — each letter in its only legal position

Key Takeaways

þ (thorn) = voiceless 'th' of thin; ð (eth) = voiced 'th' of this. Same mouth, different throat-buzz.
You already make both sounds in English — the challenge is awareness, not articulation, because English hides the choice.
þ only begins words/morphemes (það, þú, þrír); ð only appears medially or finally (maður, góður, með, við). Never the reverse.
Position predicts voicing: a word-initial "th" is voiceless þ; a medial or final "th" is voiced ð.
The two letters are never interchangeable — they are distinct letters in distinct positions.

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