Zhang and Yang (2007:97) has an interesting remark on consecutive neutral tones within certain three-character words (三字組詞):
(Translation) Should both of the latter two syllables within a three-character word possess the neutral tone, then the pitch of the neutral tone in ...
They are pronounced as 2-3 but only if they are within the same word boundary. If not, they are still pronounced as 3-3. I have given this example before:(一桶)(柳橙)。桶and柳are both third tone. Because they are in different word boundaries, there is no tone sandhi. They are pronounced as 3-3, or, more accurately, 3h-3h.
The rule of thumb is the following.
When indexing it is yi1. For example
一楼 (first floor)
一声 (first tone)
第一 (the first)
一次世界大战 (World War I)
When counting （the same rule as 不）
it is yi4 when followed by 1, 2, 3 tone
it is yi2 when followed by 4 tone
For others, mostly yi1. For example
As a ...
This is a difficult problem to address, because 等等 apparently fits one of the criteria for neutral tone, but at the same time there is tone sandhi for two conjoint third-tone words. The following attempts to resolve the conflict between the two rules:
The pronunciation of 33 words
In my explanation below, I use 1 through 4 to indicate the first to fourth ...
as in the typical tonal sandhi of two consecutive 3rd tones, like 老板 (lao2ban3).
However I wouldn't outright exclude your first suggestion deng2deng0, as it might be pronounced like that in fast speech, or in the middle of a sentence.
The Pinyin for 蒙古 is written like this in ABC:
Notice the dot under the letter E, this is an indicator that this word is read with tone sandhi. The tone sandhi rules dictate that meng3 gu3 be read:
meng2 gu3 (méng gǔ)
Another factor that may add to your confusion is the fact that the standard pronunciation in Taiwanese Mandarin is different. For ...
(This was originally a part of my answer on another question concerning tone sandhi AND neutral tones. I feel my explanation below on just tone sandhi befits here more. Consider this a slight extension to the accepted answer.)
The pronunciation of words consisting of more than two adjacent third-tone characters depends on correct parsing.
E.g. 1 老/總統 333 >...
The obligate tone sandhi for consecutive third-tones are rendered as follows:
In particular, the 333 -> 223 change in 很有品味 is explained here.
Possible facultative tone sandhi in 很有 in quick speech include:
For all 很有XX examples: blurring of tones (quasi-neutral, as explained here; to ...
我很高兴 (wǒ hěn gāoxìng) in Mandarin Chinese is pronounced in the following tones:
It's exactly as you wrote. Well done!
About tone sandhi, you can find a very simple explanation in Chinese at the following link: