13-Letter Words Matching ________TN___

There are 12 13-letter words that match ________TN___. 5 are common words, such as COLORFASTNESS and IMPERFECTNESS. A rarer one is PERMANENTNESS. 12 words contain a doubled letter.

Full list 12

colorfastnessimperfectnessincorrectnessmaladroitnesssteadfastnessdifferentnessincessantnessdownrightnessincorruptnesslightfastnessoversweetnesspermanentness

About this list

Words
12 (5 common words)
Common example
colorfastness
Rare example
permanentness
Doubled letters
12
Ending in S
12

Questions

How many 13-letter words matching ________tn___ are there?

12. 5 of them are common words.

What is a common example?

COLORFASTNESS is among the common words in this set.