"A sound change, in historical linguistics, is a change in the pronunciation of a language."
The systematic sound changes that occur in a language over time.
Phoneme: The smallest unit of sound in a language that can change the meaning of a word.
Allophone: The variations of a phoneme that occur due to the phonetic environment or dialect of a language.
Syllable: A unit of sound in a word that includes a vowel sound and may have one or more consonant sounds before or after it.
Phonotactics: The set of rules that govern the allowable combinations of sounds in a language.
Segmental phonology: The study of individual speech sounds and their combination into words.
Suprasegmental phonology: The study of the features of speech that extend over more than one sound segment, such as stress, intonation, and rhythm.
Morphophonology: The study of how the phonological rules of a language interact with its morphological structure.
Phonological processes: The systematic ways in which speech sounds change or interact with each other within a language, including processes like assimilation, deletion, and insertion.
Naturalness and markedness: The concepts used to categorize phonological processes according to how common or rare they are in language.
Prosody: The overall patterns of intonation, stress, and rhythm that give naturalness and cohesion to speech.
Lexical access: The process of retrieving the sound forms of words from memory in order to produce speech.
Language acquisition: The study of how children learn the sounds and rules of their native language(s) over time.
Assimilation: A sound changes to become more like a neighboring sound in a word.
Dissimilation: A sound changes to become less like a neighboring sound in a word.
Deletion/Elision: A sound is deleted or dropped in a word.
Insertion/Epenthesis: A sound is added to a word.
Metathesis: The order of sounds in a word is switched.
Strengthening/Fortition: A sound becomes stronger or more emphatic.
Weakening/Lenition: A sound becomes weaker or less emphatic.
Vowel Reduction: A vowel sound becomes shorter or weaker.
Tone change: The pitch or intonation pattern of a word changes.
Conditional Sound Changes: A sound changes based on the presence of another sound in the word.
Compensatory Lengthening: A vowel sound becomes longer to compensate for the loss of another sound in the word.
Rhotacism: A non-rhotic sound becomes a rhotic sound.
L-vocalization: The sound of an "l" is replaced by a vowel sound.
Epenthetic Consonant: A consonant sound is added between two vowel sounds.
Metaphony: The quality of a vowel sound changes due to the influence of a neighboring consonant sound.
"A sound change can involve the replacement of one speech sound (or, more generally, one phonetic feature value) by a different one (called phonetic change) or a more general change to the speech sounds that exist (phonological change)."
"A sound change can eliminate the affected sound, or a new sound can be added."
"The term 'alternation' refers to changes that happen synchronically (within the language of an individual speaker, depending on the neighboring sounds) and do not change the language's underlying system."
"The term 'sound change' refers to diachronic changes, which occur in a language's sound system. On the other hand, 'alternation' refers to changes that happen synchronically."
"For example, the -s in the English plural can be pronounced differently depending on the preceding sound, as in bet[s], bed[z], which is a form of alternation, rather than sound change."
"Sound changes can be environmentally conditioned if the change occurs in only some sound environments, and not others."
"Apparent exceptions to regular change can occur because of dialect borrowing, grammatical analogy, or other causes known and unknown."
"The Neogrammarian linguists of the 19th century introduced the term sound law to refer to rules of regular change, perhaps in imitation of the laws of physics."
"Research on sound change is usually conducted under the working assumption that it is regular, which means that it is expected to apply mechanically whenever its structural conditions are met."
"The expectation of their regularity or absence of exceptions is of great heuristic value by allowing historical linguists to define the notion of regular correspondence by the comparative method."
"Real-world sound changes often admit exceptions, but the expectation of their regularity or absence of exceptions is of great heuristic value."
"Each sound change is limited in space and time and so it functions in a limited area (within certain dialects) and for a limited period of time."
"For those and other reasons, the term 'sound law' has been criticized for implying a universality that is unrealistic for sound change."
"A sound change that affects the phonological system or the number or the distribution of its phonemes is a phonological change."
"Some changes are described as 'sporadic' and so they affect only one or a few particular words, without any apparent regularity."
"Sound changes can be environmentally conditioned if the change occurs in only some sound environments, and not others."
"The expectation of their regularity or absence of exceptions is of great heuristic value by allowing historical linguists to define the notion of regular correspondence by the comparative method."
"It is expected to apply mechanically whenever its structural conditions are met, irrespective of any non-phonological factors like the meaning of the words that are affected."
"Research on sound change is usually conducted under the working assumption that it is regular."