The phonological history of English consonants is part of the phonological history of the English language

Phonological history of the English language

The phonological history of English describes changing phonology of the English language over time, starting from its roots in proto-Germanic to diverse changes in different dialects of modern English....

 in terms of changes in the phonology

Phonology

Phonology is, broadly speaking, the subdiscipline of linguistics concerned with the sounds of language. That is, it is the systematic use of sound to encode meaning in any spoken human language, or the field of linguistics studying this use...

 of consonant

Consonant

In articulatory phonetics, a consonant is a speech sound that is articulated with complete or partial closure of the vocal tract. Examples are , pronounced with the lips; , pronounced with the front of the tongue; , pronounced with the back of the tongue; , pronounced in the throat; and ,...

s.

• The wine–whine merger is the merger of /hw/ (or /ʍ/, spelt wh) with /w/. It occurs in the speech of the great majority of English speakers.
• The hole–whole merger is the replacement of /hw/ with /h/ before the vowels /oː/ and /uː/ which occurred in Old English.
• The yew–hew merger is a process that causes the cluster /hj/ to be reduced to /j/.
• The hl-cluster, hr-cluster and hn-cluster reductions are three reductions that occurred in Middle English that caused the loss of /h/ from the initial consonant clusters /hl/, /hr/ and /hn/.

• Yod dropping is the elision
  Elision
  Elision is the omission of one or more sounds in a word or phrase, producing a result that is easier for the speaker to pronounce...
  
   of the sound [j].
• Yod coalescence changes the clusters [dj], [tj], [sj] and [zj] into [dʒ], [tʃ], [ʃ] and [ʒ] respectively.

• The rap–wrap merger is a reduction that causes the historical initial cluster /wr/ to be reduced to /r/.
• The not–knot merger is a reduction that causes the historical initial cluster /kn/ to be reduced to /n/.
• The nome–gnome merger is a reduction that causes the historical initial cluster /ɡn/ to be reduced to /n/.

• Final consonant-cluster reduction is the nonstandard reduction of final consonant clusters in English
  English language
  English is a West Germanic language that arose in the Anglo-Saxon kingdoms of England and spread into what was to become south-east Scotland under the influence of the Anglian medieval kingdom of Northumbria...
  
   occurring in African American Vernacular English
  African American Vernacular English
  African American Vernacular English —also called African American English; less precisely Black English, Black Vernacular, Black English Vernacular , or Black Vernacular English —is an African American variety of American English...
  
   and Caribbean English
  Caribbean English
  Caribbean English is a broad term for the dialects of the English language spoken in the Caribbean, most countries on the Caribbean coast of Central America, and Guyana. Caribbean English is influenced by the English-based Creole varieties spoken in the region, but they are not the same. In the...
  
  .
• The Plum–plumb merger is the reduction of the final cluster /mb/ to /m/.

Ng coalescence (or the singer–finger split) is the name given to a sound change in the history of English

English language

English is a West Germanic language that arose in the Anglo-Saxon kingdoms of England and spread into what was to become south-east Scotland under the influence of the Anglian medieval kingdom of Northumbria...

 by which word-final [ɡ] was deleted after [ŋ] in words like sing; this sound change happened around the end of the 16th century.

As a result of Ng coalescence, Middle English

Middle English

Middle English is the stage in the history of the English language during the High and Late Middle Ages, or roughly during the four centuries between the late 11th and the late 15th century....

 [sɪŋɡ] sing came to be pronounced [sɪŋ].