15-Letter Words Matching S_________O____

There are 18 15-letter words that match S_________O____. 4 are common words, such as SANCTIMONIOUSLY and SLAUGHTERHOUSES. A rarer one is SYMPATHECTOMIES. 3 words contain a doubled letter.

Full list 18

sanctimoniouslyslaughterhousessuperstitiouslysurreptitiouslysalpingectomiesserendipitouslysesquicarbonatesuperheterodynesuperpatriotismsedimentologiessedimentologistsigmoidoscopiessplendiferouslysubreptitiouslysubstitutionarysubterraneouslysuccinylcholinesympathectomies

About this list

Words
18 (4 common words)
Common example
sanctimoniously
Rare example
sympathectomies
Doubled letters
3
Ending in S
5

Questions

How many 15-letter words matching s_________o____ are there?

18. 4 of them are common words.

What is a common example?

SANCTIMONIOUSLY is among the common words in this set.