15-Letter Words Matching ___EM__________

There are 18 15-letter words that match ___EM__________. 8 are common words, such as CEREMONIOUSNESS and CINEMATOGRAPHER. A rarer one is REMEMBERABILITY. In this set, I is the most frequent open letter (17 words). 6 words contain a doubled letter.

Full list 18

ceremoniousnesscinematographercinematographicdisembarkationsdisembowelmentsextemporizationindemnificationundemonstrativedisembarrassingephemeralnessesextemporarinessintemperatenessmetempsychosistschematizationsdefeminizationsextemporisationnovemdecillionsrememberability

About this list

Words
18 (8 common words)
Common example
ceremoniousness
Rare example
rememberability
Doubled letters
6
Ending in S
9
Most frequent letter
I (17)

Questions

How many 15-letter words matching ___em__________ are there?

18. 8 of them are common words.

What is a common example?

CEREMONIOUSNESS is among the common words in this set.