15-Letter Words Matching ________TN_____

There are 12 15-letter words that match ________TN_____. 5 are common words, such as COLORFASTNESSES and IMPERFECTNESSES. A rarer one is PERMANENTNESSES. 12 words contain a doubled letter.

Full list 12

colorfastnessesimperfectnessesincorrectnessesmaladroitnessessteadfastnessesincessantnessesdifferentnessesdownrightnessesincorruptnesseslightfastnessesoversweetnessespermanentnesses

About this list

Words
12 (5 common words)
Common example
colorfastnesses
Rare example
permanentnesses
Doubled letters
12
Ending in S
12

Questions

How many 15-letter words matching ________tn_____ are there?

12. 5 of them are common words.

What is a common example?

COLORFASTNESSES is among the common words in this set.