14-Letter Words Matching __________ER__

There are 20 14-letter words that match __________ER__. 3 are common words, such as BUTTERFINGERED and COUNTEROFFERED. A rarer one is STEREOISOMERIC. In this set, E is the most frequent open letter (18 words). 6 words contain a doubled letter.

Full list 20

butterfingeredcounterofferedsledgehammeredasthenospheresergocalciferolmagnetospheresmagnetosphericpartridgeberrysubatmosphericarchaebacteriaasthenosphericcorynebacteriacounterordereddiastereomericenterobacteriamultichamberedoverengineeredposterolateralschoolmasterlystereoisomeric

About this list

Words
20 (3 common words)
Common example
butterfingered
Rare example
stereoisomeric
Doubled letters
6
Ending in S
2
Most frequent letter
E (18)

Questions

How many 14-letter words matching __________er__ are there?

20. 3 of them are common words.

What is a common example?

BUTTERFINGERED is among the common words in this set.