12-Letter Words Matching _R_________M

There are 18 12-letter words that match _R_________M. 3 are common words, such as PRASEODYMIUM and PROTACTINIUM. A rarer one is TRIMETHOPRIM. In this set, I is the most frequent open letter (16 words). 2 words contain a doubled letter.

Full list 18

praseodymiumprotactiniumtransvestismfraternalismpragmaticismprocommunismpropagandismprothalamiumtransformismtransuraniumtriumphalismtroglodytismarchesporiumbronchospasmcryptorchismergastoplasmgreenbackismtrimethoprim

About this list

Words
18 (3 common words)
Common example
praseodymium
Rare example
trimethoprim
Doubled letters
2
Ending in S
0
Most frequent letter
I (16)

Questions

How many 12-letter words matching _r_________m are there?

18. 3 of them are common words.

What is a common example?

PRASEODYMIUM is among the common words in this set.