Internal and external sandhi

Sandhi can be either

• internal, at morpheme boundaries within words, such as syn- + pathy: sympathy, or
• external, at word boundaries, such as the pronunciation "tem books" for ten books in some dialects of English. The linking /r/ process of some dialects of English ("I saw-r-a film" in British English) is a kind of external sandhi, as are French liaison (pronunciation of usually silent final consonants of words before words beginning with vowels) and Italian raddoppiamento fonosintattico (lengthening of initial consonants of words after certain words ending in vowels).

It may be extremely common in speech, but sandhi (especially external) is typically ignored in spelling, as is the case in English (exceptions: the distinction between a and an; the prefixes con-, en-, in- and syn- muting their *n- to *m- before -b*, -m* or -p*). Sandhi is, however, reflected in the orthography of Sanskrit, Sinhala, Telugu, Marathi, Pali and some other Indian languages, as with Italian in the case of compound words with lexicalised syntactic gemination.

External sandhi effects can sometimes become morphologised (apply only in certain morphological and syntactic environments) as in Tamil^[1][2] and, over time, turn into consonant mutations.

Tone sandhi

Most tonal languages have tone sandhi in which the tones of words alter according to certain rules. An example is the behavior of Mandarin Chinese; in isolation, tone 3 is often pronounced as a falling-rising tone. When a tone 3 occurs before another tone 3, however, it changes into tone 2 (a rising tone), and when it occurs before any of the other tones, it is pronounced as a low falling tone with no rise at the end.

An example occurs in the common greeting 你好 nǐ hǎo (with two words containing underlying tone 3), which is in practice pronounced ní hǎo. The first word is pronounced with tone 2, but the second is unaffected.

Celtic languages

In Celtic languages, the consonant mutation sees the initial consonant of a word to change according to its morphological or syntactic environment. Following are some examples from Breton, Irish, Scottish Gaelic, and Welsh:

French

The French liaison, in which a word-final consonant that is normally silent when occurring at the end of a phrase or before another consonant, is pronounced as if part of the next word when followed by a vowel, can be considered a form of external sandhi. For example, deux frères (two brothers) is pronounced /dø fʁɛʁ/ with a silent ⟨x⟩, and quatre hommes (four men) is pronounced /katʁ ɔm/, but deux hommes (two men) is pronounced /dø‿zɔm/.

Japanese

In Japanese phonology, sandhi is primarily exhibited in rendaku (consonant mutation from unvoiced to voiced when not word-initial, in some contexts) and conversion of つ or く (tsu, ku) to a geminate consonant (orthographically, the sokuon っ), both of which are reflected in spelling – indeed, the っ symbol for gemination is morphosyntactically derived from つ, and voicing is indicated by adding two dots as in か／が ka, ga, making the relation clear. It also occurs much less often in renjō (連声), where, most commonly, a terminal /n/ on one morpheme results in an /n/ (or /m/) being added to the start of the next morpheme, as in 天皇: てん ＋ おう → てんのう (ten + ō = tennō); that is also shown in the spelling (the kanji do not change, but the kana, which specify pronunciation, change).

Korean

Korean has sandhi which occurs in the final consonant or consonant cluster, such that a morpheme can have two pronunciations depending on whether or not it is followed by a vowel. For example, the root ‘읽’ /ik/, meaning ‘read’, is pronounced /ik/ before a consonant as in ‘읽다’ /ik.ta/, is pronounced like /il.k/ before vowels, as in, 읽으세요 /il.kɯ.se̞.jo/, meaning ‘please read’. Some roots can also aspirate following consonants, denoted by the letter ㅎ (hieut) in the final consonant. This causes "다" /tɐ/ to become /tʰɐ/ in 않다 /ɐntʰɐ/ ‘to not be’.^[3]