# Can we define what is an algebra and what is another?

Is it safe to say that linear algebra is "an algebra" and that abstract algebra is another algebra? Is an algebra also a set or something else?

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You may find the Wikipedia article on Universal Algebra useful. :) – Haskell Curry Mar 2 '13 at 7:16
I've voted to reopen. The title question itself is unclear, but it seems clear to me from the elaboration that OP has heard the term "an algebra" and is trying to reconcile this with subject names like "linear algebra" and "abstract algebra". – alex.jordan Mar 3 '13 at 21:30
@alex.jordan I can confirm this is the case. – Programmer 400 Mar 4 '13 at 8:44

"Algebra" means several things, all of which originate from an Arabic term "al jebr" from somewhere around the 9th century, which means something like "the bringing together of parts".

One modern meaning is that "algebra" is some formal system for manipulating symbols. High school "algebra" meets this meaning. "Linear algebra" also fits this meaning, as does "abstract algebra".

Another meaning is that "an algebra" is a vector space where there is a way to multiply two vectors together to result in another vector. This multiplication need not be commutative or associative, but it does need to conform to distributive laws.

If you've seen something referred to as "an algebra" somewhere, it is most likely not referring to a subject class (like high school algebra or linear algebra) but rather some specific vector space equipped with multiplication.

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I would add that "an algebra" refers to any variant of concepts like groups and rings in abstract algebra, mainly to any collection of n-ary operations. – Loki Clock Mar 2 '13 at 7:33