台語（台灣話）又稱為台灣閩南語，屬於漢語族 閩語支 閩南語 的泉漳片，其發音與福建廈門話、漳州話最為接近。
Taiwanese (also referred to as Taiwanese Hokkien or Taiwanese Minnan) is generally similar to the speech of Quanzhou (泉州), zhangzhou (漳州), and Amoy (廈門),
Taiwanese is a tonal language (聲調語言) with extensive tone sandhi rules (變調規則). In the traditional analysis, there are eight "tones", numbered from 1 to 8. Strictly speaking, there are only five tonal contours. But as in other Chinese varieties, the two kinds of stopped syllables (入聲) are considered also to be tones and assigned numbers 4 and 8. In Taiwanese tones 2 and 6 are the same, and thus duplicated in the count.
The following table, which is quoted from English Wikipedia, and originally from Soli Wu's Mandarin-Taiwanese Comparative Living Dictionary (吳守禮 編著之 國臺對照活用辭典), shows the eight tones in Taiwanese (note: the 2nd tone sounds exactly like the 6th tone) as well as the slight difference between Taipei speech and Tainan speech -- 下表標註各聲調的調值，並顯示台北腔與台南腔略有不同：
Examples of the tones of Taiwanese: 衫 saⁿ, 短 té, 褲 khò͘, 闊 khoah, 人 lâng, 矮 é, 鼻 phīⁿ, 直 ti̍t. (Note: Tone sandhi rules do not apply in this sentence.)
The 1st tone (e.g. 衫, 獅, 君, 番) is read as high as (55) or (44).
The 2nd tone (e.g. 短, 虎, 滾, 反) is read as falling (51) or high falling (53).
The 3rd tone (e.g. 褲, 豹, 棍, 販) is read as low falling (31) or (21) or just low (11).
The 4th tone (e.g. 闊, 鱉, 骨, 法) is read as mid stopped (32) or (3ʔ) or lower stopped (21) or (2ʔ).
The 5th tone (e.g. 人, 猴, 裙, 煩) is read as rising (14) or (24) or (25).
The 6th tone (e.g. 矮, 狗, 滾, 反) is read by most Taiwanese people in the same way as the 2nd tone.
The 7th tone (e.g. 鼻, 象, 郡, 犯) is read as mid-pitched (33).
The 8th tone (e.g. 直, 鹿, 滑, 罰) is read as high stopped (4ʔ) or (5ʔ).
下圖（取自 Wikipedia）為台語八聲調之圖示：在台灣，大部分地區第六聲調與第二聲調類同，只在部分地區如鹿港等地仍保有原第六聲調 -- See the following diagram, which shows the Taiwanese tones, close to Taipei values:
在探討如何「變調」之前，先要知道，在什麼情況下應唸本調；換言之，應唸本調（而不變調）的字----或該字在「語句／語詞」中的位置----有下列三種，不受「變調規則」影響。 The following syllables are unaffected by tone sandhi:
- The final syllable in a sentence, noun (including single syllable nouns, but not pronouns), number, time phrase (i.e. today, tomorrow, etc.), spatial preposition (i.e. on, under), or question word (i.e. who, what, how) [Note: I don't think we have "spatial prepositions" in Taiwanese, but we do have "spatial postpositions", e.g. [山] 頂, [崁] 下 or 腳, [市] 內, etc.]
- The syllable immediately preceding the possessive particle 的 (ê) or a neutralized tone. In POJ, this is the syllable before a double hyphen, e.g., 王先生 (Ông--sian-siⁿ)
- Some common aspect markers: 了 (liáu), 好 (hó), 完 (oân), 煞 (soah)
台語的變調規則，可從上面的「連續變調示意圖」得到化繁為簡的初步理解。例如：第一聲變調後說 (唸) 成第七聲；第七聲變調後說 (唸) 成第三聲；第三聲變調後說 (唸) 成第二聲；第二聲則有兩種情形，偏泉腔變成第五聲，而偏漳腔變成第一聲；至於第五聲，偏泉腔會變成第三聲，而偏漳腔會變成第七聲。
這裡所說的「非入聲字」的變調規則，除了依上圖所示，可以理出一些頭緒，也可從我所繪製的這張圖 (see below) 得到一目瞭然的「直覺式／聲調圖像化」的理解：
- If the original tone number is 1, pronounce it as tone number 7.
(e.g. the first 燒 in the phrase "燒燒").
- If the original tone number is 7, pronounce it as tone number 3.
(e.g. the first 老 in the phrase "老老")
- If the original tone number is 3, pronounce it as tone number 2.
(e.g. the first 笑 in the phrase "笑笑")
- If the original tone number is 2, pronounce it as tone number 1 (Zhangzhou/Tainan speech) or 5 (Quanzhou/Taipei speech).
(e.g. the first 冷 in the phrase "冷冷")
- If the original tone number is 5, pronounce it as tone number 7 (Zhangzhou/Tainan speech) or 3 (Quanzhou/Taipei speech).
(e.g. the first 紅 in the phrase "紅紅")
For these rules and the examples, see the chart (diagram) that I've made and posted above.
And there are some more rules and examples as follows:
- If the original tone number is 4 and the final consonant is not h (that is, it is p, t, or k), pronounce it as tone number 8.
(e.g. the first 澀 in the phrase "澀澀" )
- If the original tone number is 8 and the final consonant is not h (that is, it is p, t, or k), pronounce it as tone number 4.
(e.g. the first 直 in the phrase "直直")
- If the original tone number is 4 and the final consonant is h, pronounce it as tone number 2.
(e.g. the first 拍 in the phrase "拍拍")
- If the original tone number is 8 and the final consonant is h, pronounce it as tone number 3.
(e.g. the first 熱 in the phrase "熱熱")
上面所提及的「燒燒／老老／笑笑／冷冷／紅紅」等語詞，是一些「非入聲字」的變調實例；而「澀澀／直直／拍拍／熱熱」等，則屬於「入聲字」的變調實例了。請參閱下圖。 (For the tone sandhi rules of tones 4 and 8, see the chart below)：
The additional rules can be classified as "double tone sandhi", "triple tone sandhi", "tone sandhi before the suffix á (仔)", etc. For more information about Taiwanese tone sandhi, you and I can easily look it up in Chinese Wikipedia and English Wikipedia; of course, we can find and read many more professional articles on other websites, as well.