Stema or Stemma: How To spell?

The word Stema is misspelled against Stemma, a noun meaning "One of the facets of a compound eye of any arthropod."

Stemma has double "mm" is mispronounced as "m"
Remember double 'MM' in between the strings ste & a which should not be misspelled with single 'M'
Wrong Spelling:  ste-m-a 
Correct Spelling:  ste-mm-a 
Explore spell check of Stemma to spell without errors.

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