13-Letter Words Matching I_____L______

There are 18 13-letter words that match I_____L______. 5 are common words, such as IMMUNOLOGICAL and IMMUNOLOGISTS. A rarer one is INVIGILATIONS. In this set, N is the most frequent open letter (18 words). 8 words contain a doubled letter.

Full list 18

immunologicalimmunologistsinstallationsinstillationsirresolutionsinsufflationsinterclavicleisoagglutinininfibulationsinitialnessesinosculationsinterelectroninterglacialsinterplantinginterpleadersinterpleadinginveiglementsinvigilations

About this list

Words
18 (5 common words)
Common example
immunological
Rare example
invigilations
Doubled letters
8
Ending in S
12
Most frequent letter
N (18)

Questions

How many 13-letter words matching i_____l______ are there?

18. 5 of them are common words.

What is a common example?

IMMUNOLOGICAL is among the common words in this set.