Thirtenth or Thirteenth: How To spell?
The word Thirtenth is misspelled against Thirteenth, a noun meaning "The interval comprising an octave and a sixth."
Thirteenth has double "ee" is mispronounced as "e"Remember double 'EE' in between the strings Thirt & nth which should not be misspelled with single 'E'
Wrong Spelling:  Thirt-e-nth  Correct Spelling:  Thirt-ee-nth 
Find more wrongly spelled words of Thirteenth to spell it well.