The /d/ sound may be spelled with <d>, <de> or <dd>. The /ð/ sound is spelled <th>.
Most languages have a close equivalent of the English voiced alveolar plosive /d/, but very few have an equivalent of the voiced dental fricative of then. This sound may be replaced by /s/, /z/, /d/, /t/ or even /v/. When the contrast occurs finally, as in breed/breathe, and even more so within a post-vocalic cluster, as in breeds/ breathes, the articulatory difference may be very small; many speakers will simplify both breeds and breathes in rapid speech so that they become homophones of breeze. If learners try too hard to articulate the sounds in this environment, they may create a problem where none exists.
Interesting pairs include:
The mean density value is 0.7%, but there is a very large discrepancy in frequency between the two sounds, with /d/ occurring in over 19,000 words while /Ɵ/ occurs in just under 600. The list makes 44 semantic distinctions, a loading of 67%.
bards baths bayed bathe bladder blather bladders blathers booed booth breed breathe breeds breathes breeding breathing breeder breather breeders breathers cede seethe cedes seethes ceding seething D thee D's these dale they'll Dan than dare their dares theirs Dave they've day they den then dense thence dhow thou Di thy die thy dye thy dine thine dither thither doe though does those dough though doze those header heather headers heathers hide Hythe lade lathe laid lathe larder lather larders lathers lied lithe load loathe loading loathing loads loathes loud Louth odes oaths udder other udders others ride writhe rides writhes riding writhing seed seethe seeds seethes seeding seething side scythe sides scythes siding scything suede swathe swayed swathe teed teethe tide tithe tides tithes tied tithe wordy worthy wordier worthier wordiest worthiest wordily worthily wording Worthing
John Higgins, Shaftesbury, February 2010.