15-Letter Words Matching ____R____R_____

There are 18 15-letter words that match ____R____R_____. 4 are common words, such as PROPRIETORSHIPS and SUPERNUMERARIES. A rarer one is SUPERMAJORITIES. In this set, E is the most frequent open letter (16 words). 3 words contain a doubled letter.

Full list 18

proprietorshipssupernumerariessupersaturatingsupersaturationchurrigueresquecontrollershipsinstructorshipsproprietoriallysuperheterodynesupernaturalismsupernaturalisthypermodernistshyperpolarizingintergenerationmistranscribingsuperabsorbentssupergovernmentsupermajorities

About this list

Words
18 (4 common words)
Common example
proprietorships
Rare example
supermajorities
Doubled letters
3
Ending in S
7
Most frequent letter
E (16)

Questions

How many 15-letter words matching ____r____r_____ are there?

18. 4 of them are common words.

What is a common example?

PROPRIETORSHIPS is among the common words in this set.