13-Letter Words Matching _RT__________

There are 21 13-letter words that match _RT__________. 7 are common words, such as ARTICULATIONS and ARTIFICIALITY. A rarer one is ORTHOPTEROIDS. In this set, I is the most frequent open letter (18 words). 3 words contain a doubled letter.

Full list 21

articulationsartificialityartlessnessesorthodontistsorthogonalityorthographiesorthopaedistsarterializingarteriovenousarthroscopiesorthocephalicorthognathousorthographizeorthohydrogenarteriographyarthriticallyarthropathiesorthoepicallyorthogonalizeorthopteristsorthopteroids

About this list

Words
21 (7 common words)
Common example
articulations
Rare example
orthopteroids
Doubled letters
3
Ending in S
11
Most frequent letter
I (18)

Questions

How many 13-letter words matching _rt__________ are there?

21. 7 of them are common words.

What is a common example?

ARTICULATIONS is among the common words in this set.