5. Phonetic change and sound laws.

Sound change includes any processes of language change that affect pronunciation (phonetic change) or word structures (phonemic change). Sound change can consist of the replacement of one speech sound by another, the complete loss of the affected sound, and (rarely) even the introduction of a new sound in a place where there previously was none. Of regular sound changes, the somewhat hyperbolic term sound law is also sometimes used. This term was introduced by the Neogrammarian school in the 19th century and is still commonly applied to some historically important sound changes, such as Grimm's law (it establishes a set of regular correspondences between early Germanic stops and fricatives and the stop consonants of certain other centum Indo-European languages).

Principles of sound change. The following statements are used as state of rules in formulating sound changes as understood within the Neogrammarian model. However, for modern linguistics, they are not taken as inviolable rules; rather, they are seen as guidelines: 1. Sound change has no memory: Sound change does not discriminate between the sources of a sound. If a previous sound change causes X,Y > Y (features X and Y merge as Y), a new one cannot affect only original X's. 2. Sound change ignores grammar: A sound change can only have phonological constraints, like X > Z in unstressed syllables. It cannot drop final W, except on adjectives, or the like. The only exception to this is that a sound change may or may not recognise word boundaries, even when they are not indicated by prosodic clues. 3. Sound change is unstoppable: All languages vary from place to place and time to time, and neither writing nor media prevent this change.

Terms for changes in pronunciation. Assimilation: One sound becomes more like another, or (much more rarely) two sounds become more like each other. Example: in Latin the prefix *kom- becomes con- before an apical stop ([t d]) or [n]: contactus "touched", condere "to found, establish", connūbium "legal marriage". Metathesis: Two sounds switch places. Example: Old English thridda became Middle English third; English comfortable pronounced as if spelled comfterble. Haplology: The loss of a syllable when an adjacent (смежный, расп рядом) syllable is similar or (rarely) identical. Example: Old English Anglaland became Modern English England, or the common pronunciation of probably as ['prɒblɪ]. This change usually affects commonly used words. The word haplology itself is sometimes jokingly pronounced "haplogy". Elision, Aphaeresis, Syncope, and Apocope: All losses of sounds. Elision is the loss of unstressed sounds, aphaeresis the loss of initial sounds, apocope is the loss of final sounds, and syncope is the loss of medial sounds. Elision examples: in the southeastern United States, unstressed schwas (нейтральные гласные) tend to drop, so "American" is not /əˈmɛɹəkən/ but /ˈmɚkən/. Standard English is possum < opossum. Syncope examples: the loss of /t/ in English soften, hasten, castle, etc. Apocope examples: the final -e [ə] in Middle English words was pronounced, but is only retained in spelling as silent E.