14-Letter Words Matching I___________R_

There are 12 14-letter words that match I___________R_. 2 are common words, such as INFRASTRUCTURE and INTERPLANETARY. A rarer one is INTERPUPILLARY. In this set, T is the most frequent open letter (12 words). 4 words contain a doubled letter.

Full list 12

infrastructureinterplanetaryiatrochemistryimprovvisatoreindoctrinatorsindoctrinatoryinterferometryintelligencersinterbehaviorsinterobserversinterpellatorsinterpupillary

About this list

Words
12 (2 common words)
Common example
infrastructure
Rare example
interpupillary
Doubled letters
4
Ending in S
5
Most frequent letter
T (12)

Questions

How many 14-letter words matching i___________r_ are there?

12. 2 of them are common words.

What is a common example?

INFRASTRUCTURE is among the common words in this set.