12-Letter Words Matching _O_________M

There are 20 12-letter words that match _O_________M. 5 are common words, such as COLLECTIVISM and CONSERVATISM. A rarer one is POLYGLOTTISM. In this set, I is the most frequent open letter (18 words). 7 words contain a doubled letter.

Full list 20

collectivismconservatismcounterclaimsomnambulismvolunteerismcommensalismhomomorphismmonometalismnoctambulismpoikilothermpolymorphismvoluntaryismconnubialismhomothallismmonomorphismmonorchidismnonclassroomnonpetroleumpolycentrismpolyglottism

About this list

Words
20 (5 common words)
Common example
collectivism
Rare example
polyglottism
Doubled letters
7
Ending in S
0
Most frequent letter
I (18)

Questions

How many 12-letter words matching _o_________m are there?

20. 5 of them are common words.

What is a common example?

COLLECTIVISM is among the common words in this set.