After [...] a consonant, iou, uei, and uen are simplified as iu, ui, and un, which do not represent the actual pronunciation.
This spelling seems to have been inherited from the earlier Latinxua Sin Wenz, itself following the use in Wade-Giles. Such simplifications were likely used since [wi] is an allophone of [...
I discussed quasi-neutral tones in the fifth point of my answer to another question here. Salient points include:
Usually, a stress is placed elsewhere in the sentence. Such words are therefore weakened in their presence. See the three examples in my orginal answer for more details.
The tone sandhi is facultative (i.e. the citation tone and quasi-neutral ...
/.../ represent phonemes, which may have different realisations in different contexts/by different speakers. But, as you note, /ts/ can become voiced when unstressed and so an equally meaningful IPA transcription would distinguish the two sounds by voicedness as opposed to aspiration:
The unaspirated stops and affricates [ p, t, k, ʈʂ, ts] can become voiced ...
Standard pronunciation is indeed [x], but it can vary regionally [h ~ x].
Note, Standard Chinese does contain [h] in some monosyllabic filler words:
SC has three syllabic nasals, [m], [n], and [ŋ], which mostly occur in interjections, such as [hm] (showing contempt), [hŋ] (showing contempt), [m] (‘yes’),
[n] (‘yes’), and [ŋ] (‘yes’). Although such words ...
After z-,c-,s- (resp. zh-,ch-,sh-) pinyin i represents the syllabic consonant [z] (resp. [ʐ]):
More productive are the syllabic consonants [z] and [ʐ ], which do not
contrast with each other: [z] occurs after the dentals [ts, tsh, s], [ʐ ] after the retroflexes [ʈʂ, ʈʂh, ʂ, ʐ ]. This is exemplified in (44).
Neither [z] nor [ʐ ] occurs after the palatals [...
"High vowel" / "glide + analogous-high-vowel" are non-contrasting in Standard Chinese, and can be pronounced either way:
Chinese also lacks the contrast between V and GV, or VC and GVC, where
V is a high vowel and G is the corresponding glide, such as the pairs in (30).
The Phonology of Standard Chinese, 3.7 Allophonic ...
栖 is the simplified character of 棲
棲 has two different pinyin
(of birds) perch; roost
dwell; stay; reside; settle
[adj] restless; fidgety
兩棲 /liang3 qi1 / amphibious; dual-talented; able to work in two different lines
The video use /xi1/ instead of /qi1/, which doesn't match the dictionary. And base on the context, the dictionary ...
Once I tried to learn some Cantonese, only to find out that the teaching materials are a chaos. Every textbook author seems to use a different self invented transcription system, whereas the tone system is more complicated than in Mandarin. Sometimes the spelling doesn't fit at all, e.g. for the word "keuideih", meaning "they", people ...