Tense–lax neutralization refers to a neutralization, in a particular phonological context in a particular language, of the normal distinction between tense and lax vowels.
In some varieties of English, this occurs in particular before /ŋ/ and (in rhotic dialects) before coda/r/ (that is, /r/ followed by a consonant or at the end of a word); it also occurs, to a lesser extent, before tautosyllabic /ʃ/.
In the Pacific Northwest, especially in the Seattle area, some speakers have a merger of /ɛ/ with /eɪ/ before /ɡ/. For these speakers, words with /ɛ/ like beg, egg, Greg, keg, leg and peg rhyme with words with /eɪ/ like Craig, Hague, plague and vague.
/æ/ tensing is a process that occurs in some accents of North American and some Australian English whereby the vowel /æ/ is raised and lengthened or diphthongised in various environments. In some dialects it involves an allophonic split whilst in others it affects all /æ/s. There are dialects, however, where the split is phonological.
The trap–bath split is a vowel split whereby the Early Modern English phoneme /æ/ merged with the /ɑː/ in certain environments. It occurs mainly in southern varieties of English English, the Boston accent and the Southern Hemisphere accents (although it is somewhat variable in Australia).
The lot–cloth split is the result of a late 17th-century sound change that lengthened /ɒ/ to [ɒː] before voicelessfricatives (off, broth, cost), voiced velars (dog, long) and also before /n/ in the word gone.
The cot–caught merger is a phonemic merger that occurs in some varieties of English causing the vowel in words like cot, rock, and doll to be pronounced the same as the vowel in the words caught, talk, law, and small.
The weak vowel merger is a phonemic merger of the unstressed /ɪ/ (sometimes written as /ɨ/) with /ə/ (schwa) with in certain dialects of English. As a result of this merger the words rabbit and abbot rhyme.
Schwa syncope is the deletion of schwa. English has the tendency to delete schwa when it appears in a mid-word syllable that comes after the stressed syllable. Kenstowicz (1994) states that "... American English schwa deletes in medial posttonic syllables ...", and gives as examples words such as sep(a)rate (as an adjective), choc(o)late, cam(e)ra and elab(o)rate (as an adjective), where the schwa (represented by the letters in parentheses) has a tendency to be deleted.
The rode–road merger is the merger of /oː/ and /oə/ occurring for most English speakers. Some Welsh English speakers distinguish "rode" /roːd/ and "cole" /koːl/ from "road" /roəd/ and "coal" /koəl/.
The muse–mews merger is the merger of /yː/ and /ɪu/ occurring for most English speakers. Some Welsh English speakers distinguish "muse" /myːz/ and "due" /dyː/ from "mews" /mɪuz/ and "dew" /dɪu/.
The line–loin merger is a merger between the diphthongs /aɪ/ and /ɔɪ/ that occurs in some English dialects.