I'm not writing about accessories so much as about other slightly similar words:

adjuvant
adjunct
appurtenant
auxiliary
subsidiary
ancillary

...to name a few. I'm considering things that are added on--not the initial creation, but what is added, and, finally, even necessary in order for the initial creation to exist.

There's the school and its auxiliary gym to handle overflow; there's the factory and the ancillary plants (at least according to Webster's)...and so on.

Adjuvant is completely new to me.

My question is: Which of the words is most likely to approach the realm of being an unnecessary peripheral in your judgment? Subsidiary seems to be the least essential to me, but maybe not.

Anyway, I think it's an interesting group because there is implication that this set of brothers and sisters are less in value than their essential mothers and fathers.

[Oh, the reason this inquiry came about is today in class I used the word 'ancillary,' and one of my kids asked, "What does THAT mean? Is that another big word you want us to use in our essays?" It cracked me up! I keep telling the kids to try to explore words that go a little beyond the basic understanding of elementary school kids...average kids, that is.