Consonant th phonemes

The English diagraph represents two different phonemes in English: the voiceless dental fricative /θ/ as in "thin" and the voiced dental fricative /ð/ as in "this." Both sounds pose challenges for ESL/EFL learners, whose first languages probably lack these sounds, as both sounds are relatively uncommon throughout the world's languages. English spelling further complicates learning, since it does not distinguish the voiced and voiceless sounds. Here, slash marks like /θ/ and /ð/ denote phonemes, while angled brackets like denote letters or spelling.

1 Linguistic description

Place of articulation: The tongue tip softly touches the back of the front teeth, primarily. It can also touch more on the alveolar gum ridge above the teeth, or may protrude between the teeth, but behind the teeth is the primary locus of the sound. Thus, it is called a dental (or sometimes interdental) fricative.
Manner of articulation: This is a fricative sound, i.e., a friction sound. The air stream is forced through and around a narrowed aperture, creating a friction sound. However, these two sounds differ from other fricatives like /s/, /z/, /f/, /v/ and others, in that these sounds are produced with less energy and volume than other fricatives.
Phonation: These two sounds differ in terms of voicing, or vibration from the vocal cords (glottis). The /θ/ sound is made with no vibration, i.e., voiceless or unvoiced, just like /s/. The /ð/ sound is produced with vibration, i.e., voiced.

1.1 Cross-linguistic comparison

These sounds are rather uncommon across languages of the world.

The voiceless /θ/ occurs in Albanian, Burmese, Greek, Hebrew, Icelandic, and Welsh. A similar sound occurs in some European dialects of Spanish, where the letter <z> is lisped like /θ/, but often with a flatter tongue.
The voiced /ð/ occurs in Albanian, Arabic, Icelandic, and Welsh; it also occurs as a variant (allphone) of other sounds in Hebrew, Greek, and Spanish (the d between consonants as in adios).

The symbol /θ/ is from the Greek letter theta, while the symbol /ð/ known as eth or thagaz is from Icelandic and Anglo-Saxon writing systems, and ultimately comes from the Runic alphabet.

1.2 Teaching /θ/ and /ð/ production

Learners can start with the /s/ or /z/ sounds, and move the tongue tip behind the teeth, and to produce soft friction there. They can place their hands on their throats to feel the glottal vibration, beginning with /s/ and /z/, and then with /θ/ and /ð/.

Some learners may have been taught to mainly stick the tongue between the upper and lower teeth, which is not ideal, as this can look awkward, and they should be taught to mainly touch behind the teeth. These sounds may sound like other fricatives (especially on older telephones or other devices with poor sound quality), but learners can distinguish the sounds from others by their lower volume and energy. Most words with /θ/ are more academic and technical words that come from Greek, while /ð/ is more common in function words (minor grammatical categories such as the, this, that), and in older words derived morphologically from θ (e.g., bath - bathe), as described in Phonemes /θ/ and /ð/ in spelling. Thus, ESL/EFL learners at an intermediate or advanced level can be taught that new words that they encounter with , especially academic words, are likely words from Greek with the /θ/ pronunciation (e.g., thermodynamics, dysthymia).

Phonemes /θ/ and /ð/ in spelling

2 Practice activities and materials

Minimal pairs, which contrast a target sound with a sound that is a separate phoneme, are typical starting points for production and practice activities, particularly comparing /θ/ cf. /ð/, /θ/ cf. /s/, and /ð/ cf. /z/. These contrasts should be shown with minimal pair contrasts in syllable-initial, consonant cluster, medial, and final position. For more on types of minimal pairs activities to train listeners to discern and produce sounds, see the following.

2.1 Minimal pairs

There are only a few contrastive word pairs for /ð/ and /θ/, and some of these are old words.

initial	medial	final
thigh thy	wreaths wreathes	bath bathe breath breathe loath loathe mouth mouth(e) (e.g., to mouth off)	sheath sheathe sooth soothe teeth teethe wreath wreathe

More commonly, though, non-natives have difficulty with /θ/ and /s/.

/s/	/θ/
burst bypass ensues face moss race sick sink truce unsinkable	berth bypath enthuse faith moth wraith thick think ruth unthinkable

And they have difficulty with /ð/ and /z/:

/z/	/ð/
breeze close lays rising she's size	breathe clothe lathe writhing sheathe scythe

There are also few with a /z/ - /ʒ/ distinction (the palatal fricative as in pleasure); some of these are rare words or European place names.

medial

final

/z/	/ʒ/
Caesar composer loses ruses	seizure composure luges rouges

/z/	/ʒ/
baize brews liaise loose rues	beige Bruges Liège luge rouge

For more minimal pairs, see below.

2.2 Minimal pair sentences

To teeth(e), teething: When a baby or puppy has new teeth coming in, experiences gum and tooth soreness, and needs to chew on something to relieve the discomfort.

When a baby’s new teeth come in, she experiences teething pains, and has to teethe on something.

2.3 Tongue twisters

Try the following tongue twisters.

Thin sticks, thick bricks.
Pacific Lithograph
Three free throws.
Six thick thistle sticks
Red leather, yellow leather.
(I think that) this myth is a mystery to me.
Cassie threw Cathy a thick math book.
The Leith police dismisseth^[1] us.
Freddy Thrush flies through thick fog.
Thelma sells thick thistles near the theater.
He thinks he’d rather get married when he’s thirty-three years old.
Is this your sister's sixth zither, sir?
Three free thugs set three thugs free.
Faith's face cloth, Faith's face cloth, Faith's face cloth.
Thirty-three thousand people think that Thursday is their thirtieth birthday.
I’d rather not bother my seething brothers for a few farthings.
There are thirty thousand feathers on the thrush’s throat.
Mr. Dithers goes hither and thither to lather his withering plants.
The sixth sick sheik's sixth sheep's sick.
Nathan sews with a thimble, while Ethan throws things at some sinners.
The seething seas ceaseth and twice the seething seas sufficeth us.

Extended tongue twisters

1.	A thought... I thought a thought. But the thought I thought Wasn't the thought I thought I thought. If the thought I thought I thought, Wasn’t the thought I thought, I wouldn't have thought so much.
2.	She is a thistle-sifter. She has a sieve of unsifted thistles and a sieve of sifted thistles and the sieve of unsifted thistles she sifts into the sieve of sifted thistles because she is a thistle-sifter.
3.	Theophilus Thadeus Thistledown, the successful thistle-sifter, while sifting a sieve-full of unsifted thistles, thrust three thousand thistles through the thick of his thumb. Now, if Theophilus Thadeus Thistledown, the successful thistle-sifter, thrust three thousand thistles through the thick of his thumb, see that thou, while sifting a sieve-full of unsifted thistles, thrust not three thousand thistles through the thick of thy thumb.

3 Distribution: /ð/ and /θ/ in spelling patterns

See Phonemes /θ/ and /ð/ in spelling

4 More minimal pairs

4.1 /s/ and /θ/

initial	medial	final
cymbal thimble sane thane sank thank saw thaw sawn thorn seam theme seines thanes serum theorem sick thick sicken thicken sickly thickly sickness thickness sigh thigh sin thin sink think sinkable thinkable sinking thinking sinker thinker sin thin sinner thinner soar Thor sole thole some thumb song thong sort thought souse south suds thuds sues thews sum thumb summed thumbed summing thumbing sump thump sums thumbs sunder thunder sundered thundered sundering thundering surd third	besought bethought burst berthed Essex ethics frost frothed tensely tenthly sinned thinned sinning thinning unsinkable unthinkable useful youthful usefully youthfully usefulness youthfulness	bass bath bypass bypath ensues enthuse face faith force forth gross growth kiss kith Miss myth moss moth mouse mouth Norse north pass path Perth purse race wraith sluice sleuth tense tenth truce truth use youth worse worth

4.2 /z/ and /ð/

initial	medial	final
zee thee z’s these Zen then	breezed breathed breezing breathing closed clothed closing clothing rising writhing seized seethed seizing seething teased teethed teasing teething wizard withered	baize bathe boos booth breeze breathe close clothe lays lathe lies lithe lows loathe rise writhe seize seethe she's sheathe size scythe sous soothe sways swathe tease teethe ties tithe

In some dialects of British and New England English, "with" is pronounced with /ð/ instead of /θ/, leading to a minimal pair of "whiz - with."

4.3 /θ/ versus /z/

initial	medial	final
thing zing think zinc	(none)	berth burrs both bows death Des doth does earth errs eighteenth eighteens eleventh elevens faith phase fifteenth fifteens filth fills firth firs / furs fourteenth fourteens fourth fours growth grows hath has health hells heath he's hundredth hundreds Keith keys Keuth quays	loth lows millionth millions mouth mows myth Ms 'neath knees nineteenth nineteens ninth nines north gnaws oath O's oath owes path pars path parse Perth purrs ruth rues ruth ruse saith says seventeenth seventeens seventh sevens sleuth slews sloth sloes / slows	sooth sous south sows teeth T's teeth teas teeth tease tenth tens thirteenth thirteens tilth tills tooth twos trillionth trillions truth trews warmth warms wealth wells withe whiz worth whirrs wraith raise wraith rays youth U's youth use