12-Letter Words Matching A_________U_

There are 22 12-letter words that match A_________U_. 4 are common words, such as ADVANTAGEOUS and ADVENTITIOUS. A rarer one is ATHEROMATOUS. In this set, O is the most frequent open letter (21 words). 2 words contain a doubled letter.

Full list 22

advantageousadventitiousambidextrousasynchronousacanthaceousachlamydeousadscititiousamphicoelousamphitheciumamphitropousandrocliniumanemophilousapocynaceousargillaceousaltitudinousamentiferousankylosaurusanthophilousappressoriumarchesporiumascomycetousatheromatous

About this list

Words
22 (4 common words)
Common example
advantageous
Rare example
atheromatous
Doubled letters
2
Ending in S
18
Most frequent letter
O (21)

Questions

How many 12-letter words matching a_________u_ are there?

22. 4 of them are common words.

What is a common example?

ADVANTAGEOUS is among the common words in this set.