Pengyou (friend) - tones

[eddiewould]

Hi,

I've noticed when I look up "pengyou" (friend) in Pleco, it comes up as péngyou (i.e 1st tone, neutral tone). I've got another Chinese dictionary at home (not to be trusted however) which concurs.

However my Chinese friends (and also the internet) say it should be péngyǒu. Also, when I look at the characters individually in Pleco, 'you' comes up as yǒu i.e. 3rd tone.

What gives?

 

[scykei]

It's a bit weird how the neutral tone works. The thing is, certain compounds cause some tone sandhi changes.

Here are some other examples of compounds which I can think of that do this:
石頭 is shi2tou when 頭 is usually tou2.
愛人 is ai4ren when 人 is usually ren2.
清楚 is qing1chu when 楚 is usually chu3.
困難 is kun4nan when 難 is usually nan2.

It's very easy to overlook these minor tone changes if you don't pay attention though.

EDIT: I found an interesting article about the neutral tone: http://www.learnchineseabc.com/chinese- ... l-tone.htm