13-Letter Words Matching _________OI__

There are 12 13-letter words that match _________OI__. 2 are common words, such as HYPERTHYROIDS and THOROUGHGOING. A rarer one is PLEROCERCOIDS. 2 words contain a doubled letter.

Full list 12

hyperthyroidsthoroughgoingamphidiploidsconservatoirespermatozoidsxanthochroismamphidiploidycysticercoidsfianchettoinghydrocolloidsorthopteroidsplerocercoids

About this list

Words
12 (2 common words)
Common example
hyperthyroids
Rare example
plerocercoids
Doubled letters
2
Ending in S
7

Questions

How many 13-letter words matching _________oi__ are there?

12. 2 of them are common words.

What is a common example?

HYPERTHYROIDS is among the common words in this set.