Cisoid or Cissoid: How To spell?
The word Cisoid is misspelled against Cissoid, a noun meaning "A curve invented by Diocles, for the purpose of solving two celebrated problems of the higher geometry; viz., to trisect a plane angle, and to construct two geometrical means between two given straight lines."
Cissoid has double "ss" is mispronounced as "s"Remember double 'SS' in between the strings ci & oid which should not be misspelled with single 'S'
Wrong Spelling:  ci-s-oid  Correct Spelling:  ci-ss-oid 
Find more incorrect spellings of Cissoid to spell right way.