In English, the spelling "ch" is used to represent the Greek letter "chi" (χ) when transliterating Greek words. 
This convention stems from the way Greek words were adapted into Latin and subsequently into English. 
As a result, many English words of Greek origin feature "ch" where a "k" sound is pronounced.

In Inglish, in alignment with Modern Spanish, the letter combination "ch" only represents the sound /tʃ/.
In English words where "ch" was pronounced "k", Inglish uses either the letter "k" or "c" - simplifying the orthography.


Examples:
    Chaos: From Greek χάος
    Character: From Greek χαρακτήρ
    Chorus: Latin word from Greek χορός
    Choir: From Latin chorus, from Greek χορός
    Mechanic: From Greek μηχανικός
    Technical: From Greek τεχνικός
    Chthonic: From Greek χθόνιος

Inglish uses -k- or -c- instead:
    kâoʃ
    câractre (letters), câractor (person)
    korus
    cuîor
    mecànic
    teknical
    þónic (k is dropped, because it's not pronounced)


https://lsj.gr/wiki/χάος
https://lsj.gr/wiki/χαρακτήρ
https://lsj.gr/wiki/χορός
https://lsj.gr/wiki/μηχανικός
https://lsj.gr/wiki/τεχνικός
https://lsj.gr/wiki/χθόνιος