Conlang/Intermediate/Sounds/Sandhi rules

Sandhi (Sanskrit संधि "joining") is a number of phenomena that occur at morpheme boundaries that involve a phonological change dependent on the phonological nature or grammatical function of neighbouring morphemes.

There are two forms of sandhi. Internal sandhi involves changes within a word due to the linking of two different morphemes: syn-pathy → sympathy. This is also known as assimilation (Latin ad-simulatio → assimulatio ‘to render similar’). External sandhi is changing at word rather than inter-word morpheme boundaries: [tEm bUks] for ten books.

The word ‘sandhi’ is a term originally used to refer to a set of Sanskrit phonological processes, such as the combination of vowels at morpheme boundaries: hita-upadesha → hitopadesha, ‘friendly instruction’.

Lenition

Another form of sandhi is lenition, which means ‘softening’. This involves a movement on the sonority hierarchy from less to more sonorous. In practical terms, this can be broken down into a number of processes:

• voicing, which involves a consonant moving from unvoiced to voiced, as with /k/ → /g/
• affrication, which involves a stop becoming an affricate, as in /t/ → /ts/
• spirantization, which involves a stop or affricate becoming a fricative, as with /ts/ → /s/, or /b/ → /f/
• debuccalization, which involves moving the place of articulation, usually to the back of the mouth, such as /s/ → /h/
• deglottalization, which involves glottalized consonants losing glottalization, as with /g_>/ → /g/ and others.

Lenition is common intervocalically (between vowels).

This occurs in two forms: diachronic, meaning a change that takes place over time, and therefore does not enter into this discussion, and synchronic, meaning at one point in time. Examples of languages with synchronic lenition are:

• Sardinian (observe the example of /d/ → [D]: domu [dOmu] ‘house’ → su domu [su DOmu] ‘the house’, triggered by the definite article su)
• Various Celtic languages (observe Irish Gaelic /t_d/ → /h/: tana /t_dan@/ ‘thin’ → glé thana /ɡ_0le: han@/ ‘very thin’, an example of debuccalization)
• J.R.R. Tolkien's invented language Sindarin (/d/ → [D]: dîn, ‘silence’ → i dhîn, ‘the silence’)

This is typically triggered by a grammatical function word that ends in a vowel (Sardinian su, Sindarin i, above) or is generalized by analogy from a situation where the mutation is sometimes triggered phonologically (by being proceeded by an adjective, for example).

Fortition

The opposite of lenition is fortition. While less common, it does occur; as in the Italian /kasa/ ‘house, home’ → [ka:sa] but /a kasa/ ‘at home’ → [ak:a:sa].

Tone Sandhi

In tonal language the tones will often interact via a process called tone sandhi, where one of the tones will become another under certain situations, often under the influence of other tones.

Here a few examples from modern Chinese (mandarin, pinyin writing system) :
When any number of tone 3 syllables directly proceed a tone three syllable the first syllables will change to a tone 2.

• xiang3 mai3 hao3 ma3 -> Sandhi -> xiang2 mai2 hao2 ma3

In a string of three syllables, where a tone 2 in preceded by either tone 1 or 2, and followed by any tone but the neutral tone, the second syllable will become tone 1.

• san1 nian2 ji2 -> Sandhi -> san1 nian1 ji2

Another language exhibiting complex tone sandhi is Amoy.

the tones of the Amoy language and its tone sandhi process

Quoted from Wikipedia : Tone sandhi
"Amoy has five tones, which are reduced to two in syllables which end in a stop consonant. (These are numbered 4 and 8 in the diagram above.) Within a phonological word, all syllables but the last one change tone. Among unstopped syllables (that is, those which do not end in a stop), tone 1 becomes 7, tone 7 becomes 3, tone 3 becomes 2, and tone 2 becomes 1. Tone 5 becomes 7 or 3, depending on dialect. Stopped syllables ending in /p/, /t/, or /k/ take the opposite tone (phonetically, a high tone becomes low, and a low tone becomes high), whereas syllables ending in a glottal stop (written h in the diagram above) drop their final consonant to become tones 2 or 3."