13-Letter Words Matching ____E____C___

There are 20 13-letter words that match ____E____C___. 5 are common words, such as CONFEDERACIES and CONSERVANCIES. A rarer one is STEREOPTICONS. In this set, I is the most frequent open letter (18 words). 1 words contain a doubled letter.

Full list 20

confederaciesconservanciesegocentricityinfrequenciesmathematicianautoeroticismconcentricityconvergenciesconversancieshomoeroticismnonrestrictedoystercatcherpantechniconsconvenienciesexcrescenciesletterspacingpresentencingproteoglycansproventriculistereopticons

About this list

Words
20 (5 common words)
Common example
confederacies
Rare example
stereopticons
Doubled letters
1
Ending in S
10
Most frequent letter
I (18)

Questions

How many 13-letter words matching ____e____c___ are there?

20. 5 of them are common words.

What is a common example?

CONFEDERACIES is among the common words in this set.