15-Letter Words Matching A_______R______

There are 21 15-letter words that match A_______R______. 5 are common words, such as ADMINISTRATIONS and AROMATHERAPISTS. A rarer one is ARTERIOGRAPHIES. In this set, I is the most frequent open letter (21 words). 4 words contain a doubled letter.

Full list 21

administrationsaromatherapistsatmosphericallyautobiographersautobiographiesallelomorphismsantiallergenicsantifederalistsantiliberalismsantilibertarianantilogarithmicantimaterialismantimaterialistantimonarchicalantimonarchistsantiprogressiveantiseparatistsantitheoreticalantituberculousapolipoproteinsarteriographies

About this list

Words
21 (5 common words)
Common example
administrations
Rare example
arteriographies
Doubled letters
4
Ending in S
13
Most frequent letter
I (21)

Questions

How many 15-letter words matching a_______r______ are there?

21. 5 of them are common words.

What is a common example?

ADMINISTRATIONS is among the common words in this set.