Tone shift rule?

[DanielG]

Sometimes in words of two or three characters, the pronunciation of the last character shifts from its regular tone to a neutral tone, for example the character 少 (shao3) becomes neutral in the word 多少 (duo1shao5)  or the character 欢 (huan1) in 喜欢 (xi3huan5).  Is there a rule about such tone shifts?

[renzhe]

There are some rules, like:

- duplicated characters (姐姐, 弟弟)

- some suffixes like 子 or 头 (孩子, 石头)

With many other words, you have to learn it, like 明白. Often, both are acceptable and many native speakers will pronounce the full tone, like 喜欢 (Taiwanese typically don't use the neutral tone much).

With some words, you have to be careful, because the meaning changes based on whether the tone is neutral: 东西 can mean "thing" or "east-west", depending on whether 西 carries the first tone or not.

This thread lists many such minimal pairs.

[tooironic]

You may also find my blog post on Variant Pronunciations (which includes examples of what you were talking about under "second-syllable stress") useful.