How did Middle Chinese "hæwk" evolve into Mandarin "xué"? So I was wondering why the on'yomi reading of Japanese 学 was &quot;gaku&quot; and the Korean reading of 學 was &quot;hak&quot;, since I knew that in Mandarin, 学 was &quot;xué&quot;, which is radically different from the two.
I did some research and learned that the Middle Chinese reading of 學 was &quot;hæwk&quot; (IPA /ɦˠʌk̚/). That left me to wonder: how did Middle Chinese &quot;hæwk&quot; evolve into modern day Mandarin &quot;xué&quot;, considering that modern day Cantonese 學 is &quot;hok6&quot;?
It seems like no other Sinitic or Sino-Xenic descendants differed vastly from the original pronunciation of &quot;hæwk&quot; as much as Mandarin did. Is there a reason for Mandarin specifically differing so much as well?
Linguistically I know the least about Mandarin since I'm a heritage speaker and I didn't learn it as a language learner like I did the other languages, so I apologize if this is a stupid or bad question
I'm not an expert on historical Chinese phonology, but this doesn't seem like an uncharacteristically distant sound evolution compared to other words:
           Baxter       (Zhengzhang
           –Sagart       Shangfang)
Hanzi | Old Chinese | Middle Chinese | Mandarin
 學   |  *m-kˤruk   |      ɦˠʌk̚      |   xué
 穴   |  *[ɢ]ʷˤi[t] |      ɦwet̚      |   xué
 血   |  *m̥ˤik      |      hwet̚      |   xuè

Between Late Middle Chinese and Modern Mandarin, the final consonants /p/, /t/, /k/ were dropped. In Mandarin the only consonants a syllable can end on are n or ng.
/ɦˠ/ and /ɦw/ - back-of-the-mouth velarized and labialized fricatives, respectively, - likely shifted towards fricatives farther forward in the mouth.