Consonant phonemes /θ/ and /ð/ in spelling

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The English spelling stands for two different sounds: the voiceless /ɵ/ and voiced /ð/. “Voiced” means you feel that vibration in the throat, from the vocal cords vibrating. We will look at some hints to help you know how to pronounce . There are no absolute rules that can tell you to pronounce it as /θ/ or /ð/, but there are some very helpful guidelines. In this article, slash marks indicate phonemes, e.g., /θ/, /ð/, while angled brackets like indicate letters or spellings.

1 Introduction

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.

  • See phonemes for an introduction to these sounds.

The voiced /ð/ sound tends to occur in function words (minor grammatical words like articles, determiners, and such, so a spelling in such words is most often /ð/. This includes some words that are not used in modern English (marked with asterisks below).

the, this, that, these, those, they, than, there, therefore, thereupon, though, although, then, hither*, thither*, whither*, thee*, thy*, thou*, thyself*

A few exceptions exist to these voiced /ð/ patterns[1]. Most other content words (nouns, verbs, adjectives, adverbs) with are pronounced with /θ/. Most likely, then, when you encounter an unfamiliar word with , it will be /θ/.

2 Basic patterns

The most basic patterns for learners are the following:

  1. Function word pattern
  2. Old English suffix pattern
  3. Greek / Anglo-Saxon content word patterns (or the Elsewhere Principle)

2.1 Function word pattern: in function words = /ð/

Function words are minor words (besides content words — nouns, adjectives, adverbs, and verbs); function words include prepositions, conjunctions, particles, pronouns, pro-forms (there), articles, etc. The in function words is usually at the beginning of the word, and is often pronounced /ð/ (but not always).

articles the
pronouns, pro-forms this, that, these, those, they, than, there
prep., conj. than, therefore, thereupon, though, although, then


  1. The of the following function words is /θ/ because they are compounded from thing: anything, something, nothing, everything.
  2. The in through is pronounced /θ/. The preposition with is usually /wɪθ/ in North American English and other dialects, but /wɪð/ in some New England and British dialects.

2.2 Old English (Anglo-Saxon) suffix pattern: before Old English endings = /ð/

The before some Old English (Anglo-Saxon) suffixes and word endings is pronounced /ð/, in particular:

  • -e, -er, -ern, -en, -ing (noun)

The -e often creates verbs from nouns. In some cases we can see the original base word which has /θ/, but adding a suffix changes it to /ð/, but sometimes the original base word has disappeared from English. This -ing is a general noun suffix as in building, not the verb ending.

θ → ð θ → ð






clothing, clothier

northern, norther

The same is true of other Old English words that were derived in a similar way, but have since undergone spelling changes that obscured this process, such as fathom /fæðəm/ and smooth /smu:ð/.

Some words from Old English with /ð/ + suffix: The voiced /ð/ also occurs in words with certain endings, including Old English endings, such as words formed by adding -e to nouns to turn them into verbs. In the following table, asterisks (*) indicate older,rarer, or obsolete words.

ending examples
-e bathe, blithe, breathe, clothe, lathe, loathe, scythe, seethe, soothe, teethe, tithe , mouth(e), tithe, wreathe, writhe
-er another, bather, blithering, bother, breather, brother, dither, father, farther, further, gather, heather, hither*, leather, mother, nether*, neither, norther, northerly, other, rather, slither, smother, southerly, tether, thither*, together, weather, whether, whither*, wither, wuther*, wuthering*;

also -ier: clothier

-ern northern, southern
-en brethren*, heathen
-ie, -ee smoothie, couthie*, smoothee, prithee*
-ing (nouns) clothing, farthing*, loathing, sheathing

Also, a few other Old English words:

  1. Most adjectives formed with -y are pronounced with /θ/, except for:
    • worthy /wɔrði/, unworthy, trustworthy
  2. adjectives in -er, -est from Old English words like those forms above, e.g.,
    • farthest, furthest, smoothest, worthiest


  1. When adding other suffixes, such as verbal -ing, the pronunciation of the base word is retained in the new word:
    • /ð/: breathe → breathing, breathed
    • /θ/: sleuth → to sleuth, sleuthing, sleuthed
  2. Words with the verbal suffix -then (to create verbs from adjectives) have /θ/, such as strengthen, lengthen.

2.3 Greek / Anglo-Saxon content word patterns (Elsewhere Principle)

Except for some unusual patterns in the next section, most words in English that are content words (nouns, verbs, adjectives, adverbs) are from Greek, or from Anglo-Saxon (Old English) or medieval English, and are pronounced as /θ/. That is, unless the above conditions apply (function word, AS ending), the elsewhere is usually /θ/. For older English words, the as voiceless /θ/ is usually found in initial (beginning of word) or final (end of word), which are naturally voiceless positions[2]. Most academic or technical words in English with are from Greek, so for new academic words, one can guess that such words are pronounced with /θ/.

Old English (AS) / medieval English
Arthur, birth, booth, broth, earth, hearth, mouth, north, northwest, thank, thatch, through, Thursday, thud, throne, thousand, three, tooth, worth, ...
athletic, dysthymia, isotherm, lethal, metathesis, panthalassic, theocratic, thermos, therapist, thesis, thiamine, thyroid, ...

Note: Words with -or like author are usually from Latin, where again = /θ/.

2.4 Other languages, and unusual or exceptional patterns: = /ð, θ, t/

The following patterns are for more advanced learners. These are (1) words that come from other languages, (2) a few words from Greek or via Greek, where a following /m/ makes the voiced, or (3) a few other quirks as noted above.

2.4.1 Other words with /ð/

  • fathom, smooth

These and a few other words have [ð], as noted above, due to Old English origins or the <thm> patterns above. The word smooth is a spelling irregularity; it came from an Old English ending (smothe/smoothe), with the final -e being dropped later.

2.4.2 Non-Anglo-Saxon -ther = /θ/

Some words have similar spellings as the Old English endings, but are not from Old English. They happen to have similar spellings, but come from other languages such as Greek and German, and these words are pronounced with /θ/:

  • anther, ether, panther, zither, Luther[3]

2.4.3 = /t/

In these proper names and words (which come from other languages), the is pronounced as /t/, not as /θ/ or /ð/:

  • Esther (from Persian), Thomas (from Aramaic), * Mathilda (or Matilda; from Gothic)
  • Thai, Thailand (from Thai)
  • Thames (from Celtic)
  • thyme (from Greek via Latin and Old French, apparently with French alteration of /θ/ to /t/, as French lacks the /θ/ sound)
  • Neanderthal (from German)[4]; Luther (original German pronunciation)

2.4.4 + <y> = /θ/ in adjectives

Adding the adjective suffix <-y> generally does not change the sound of ; it generally remains /θ/.

  • froth - frothy
  • health - healthy
  • pith – pithy

2.4.5 Greek / Greceanized -thm spelling pattern

In the following words, the is voiced by the adjacent /m/. These are mostly from Greek, except algorithm (which came from Persian, but came into Greek and was adapted to the Greek spelling pattern).

  • algorithm algorithmic antilogarithm antiarrhythmic arrhythmic biorhythm dysrhythmic eurhythmic eurythmic isthmic logarithm polyrhythm rhythm logarithm logarithmic polyrhythmic rhythmic

3 Pattern summary

When you encounter words with the spelling, you can put them through the following test to determine its pronunciation:

1. Function word Is it a function word? If so, then probably voiced /ð/.
2. Old English ending Is it an Old English ending? If so, then voiced /ð/.
3. Exceptional pattern A small number of unusual words and patterns could mean /ð/, /θ/, or /t/.
4. Elsewhere rule You can probably assume it’s the voiceless /θ/ from Greek (academic words) or older non-academic English words.

4 See also

  1. Most -thy words are pronounced with /θ/, but in a few words it is pronounced with /ð/, namely: worthy, smoothy/smoothie. Some -er words are not from Old English and are pronounced /θ/, e.g., ether, Luther, panther, zither. Also note these “exceptions”: smooth /ð/ (a spelling irregularity); and names of foreign origin where is pronounced /t/: Esther, Mathilda, Thai, Thailand, Thames, Thomas.
  2. In Anglo-Saxon, the sound was voiced in invervocalic (between vowels) or medial (middle of word or syllable) positions, and was unvoiced in word-initial and word-final positions, as it is easier for the glottis to vibrate medially and to not vibrate initially or finally. This voicing rule applied regardless of whether the Anglo-Saxon words were spelled with the old letters thorn <þ> or thagaz <ð>.
  3. Actually, German does not have the /θ/ sound; Luther is pronounced more like /lutɜ/ in German, while the pronunciation of his name is Anglicized by English speakers who do not know German to /luθɜ(r)/.
  4. However, some English speakers Anglicize the pronunciation to /θ/ in Neanderthal.

4.1 Other pages