15-Letter Words Matching S_____N________

There are 17 15-letter words that match S_____N________. 5 are common words, such as SUBSTANTIATIONS and SUPERANNUATIONS. A rarer one is SUPERINFECTIONS. In this set, I is the most frequent open letter (16 words). 5 words contain a doubled letter.

Full list 17

substantiationssuperannuationssuperintendencesuperintendencysuperintendentssuperindividualsedimentologiessedimentologistsemicentennialsseroconversionsspontaneousnesssubstantialnesssubstantivenesssubstantivizingsuperencipheredsuperinductionssuperinfections

About this list

Words
17 (5 common words)
Common example
substantiations
Rare example
superinfections
Doubled letters
5
Ending in S
11
Most frequent letter
I (16)

Questions

How many 15-letter words matching s_____n________ are there?

17. 5 of them are common words.

What is a common example?

SUBSTANTIATIONS is among the common words in this set.