Tone sandhi

Tone sandhi (Zoafntiau) in Taiwanese is the process of altering the tone of a syllable depending on the surrounding words and grammatical function. Most nouns in Taiwanese do not change tone. However, almost all verbs and adjectives do change tone when not at the end of a phrase.

Basic Rules (Tone Circle)

If the original tone number is 5 (curving-up tone), pronounce it as tone number 7 (basic). (see Ciangciw-oe)
If the original tone number is 7 (basic tone), pronounce it as tone number 3 (low falling).
If the original tone number is 3 (low tone), pronounce it as tone number 2 (shouting out).
If the original tone number is 2 (shouting tone), pronounce it as tone number 1 (high).
If the original tone number is 1 (high tone), pronounce it as tone number 7 (basic).

If the original tone number is 8, pronounce it as tone number 4.
If the original tone number is 4, pronounce it as tone number 8.

See diagram and Taiwanese Hokkien#Tone sandhi for a more detailed explanation.

Examples

køf 🔊 + hioong 🔊 = Køhioong 🔊
tvar 🔊 + kao 🔊 = Tvafkao 🔊
baq 🔊 + zaxng 🔊 = bahzaxng 🔊
Taai 🔊 + oaan 🔊 = Taioaan 🔊
ki 🔊 + zhvef 🔊 = kixzhvef 🔊
bak 🔊 + ciw 🔊 = bagciw 🔊

Exceptions

most nouns
ciaf, hiaf, zef, hef, ciahniq', hiahniq'
symmih, ui symmih, (see Taiguo_Siong'iong_460-ji#Demonstrative_pronouns)
basic tone + ar. (The basic tone syllable is excepted).
surnames before siensvy 🔊: Taan`siensvy 🔊

Further details

more detailed rules have been posted at Wikipedia: Taiwanese Hokkien#Tone sandhi, esp. special cases involving suffix ar (仔) and triplication
syllables ending in "h" are usually pronounced in shouting tone, such as in bahzaxng 🔊, but not beq 🔊
khix (toxngsuu) is usually treated as if originally "khiq"

External Links

Wikipedia: Tone sandhi