Why Do Physicists Use the Term Unity Instead of 1 in Crystallography?

[denjay]

I came across this term in Elements of Modern X-ray Physics by Nielsen. I'm assuming this term isn't specific to the book (because that would be ridiculous). I've always taken math courses geared toward Physics/Engineering so some math terms were never used so this is probably one of them.

I'm assuming it is somehow equivalent to 1. I just don't know why the author did not say 1 instead of unity.

The context in which it was used was

 

[Muphrid]

It's really just a word used to sound more pretentious than saying "one." It might be handy to distinguish 1 of some unit of measure versus 1 as a pure number, but that's about it.

 

[denjay]

I suppose it makes sense to use unity instead of 1 for units. Especially in a Physics textbook.

Thank you sir and/or ma'am.

 

[DrewD]

Unity is a unitless one. It is also used extensively in ring theory so that the theorems can be extended to systems that do not use numbers. I doubt the second part is the reason in an X-ray physics book.