15-Letter Words Matching _I_________O___

There are 12 15-letter words that match _I_________O___. 3 are common words, such as DISPROPORTIONAL and MICROELECTRONIC. A rarer one is MISCEGENATIONAL. In this set, S is the most frequent open letter (11 words). 3 words contain a doubled letter.

Full list 12

disproportionalmicroelectronicnitrocellulosespithecanthropusdiastereoisomerdisproportionedhistopathologiclignocelluloseslignocellulosicmicroelectrodesmicrometeoroidsmiscegenational

About this list

Words
12 (3 common words)
Common example
disproportional
Rare example
miscegenational
Doubled letters
3
Ending in S
5
Most frequent letter
S (11)

Questions

How many 15-letter words matching _i_________o___ are there?

12. 3 of them are common words.

What is a common example?

DISPROPORTIONAL is among the common words in this set.