15-Letter Words Matching ____S___T______

There are 17 15-letter words that match ____S___T______. 4 are common words, such as BACKSCRATCHINGS and FORESIGHTEDNESS. A rarer one is TRANSUBSTANTIAL. In this set, I is the most frequent open letter (16 words). 11 words contain a doubled letter.

Full list 17

backscratchingsforesightednessnearsightednesstransportationscoinstantaneousincessantnessesperistalticallytransvestitismsbackscatteringsfetishisticallykinestheticallylongsightednessmagistraticallyoversweetnessessidesplittinglytranshistoricaltransubstantial

About this list

Words
17 (4 common words)
Common example
backscratchings
Rare example
transubstantial
Doubled letters
11
Ending in S
10
Most frequent letter
I (16)

Questions

How many 15-letter words matching ____s___t______ are there?

17. 4 of them are common words.

What is a common example?

BACKSCRATCHINGS is among the common words in this set.