# Free basis and basis?

1. May 9, 2007

### pivoxa15

1. The problem statement, all variables and given/known data
What are the differences between the two?

2. May 10, 2007

### maverick280857

Do you mean ordered basis?

3. May 10, 2007

### pivoxa15

Don't think so.

4. May 10, 2007

### quasar987

Just surfing wiki, I get the impression that there is none. Do you have a reason to believe that there is a difference?

5. May 10, 2007

### maverick280857

Yeah, looks the same to me. This is what I studied in my linear algebra course: there's something called a basis and then something called an ordered basis. A basis with an ordering of elements (somewhat like an indexing set that has been fixed which maps to elements of your basis) is called an ordered basis.

I think when you say free basis, you probably mean a basis without ordering...but thats just a wild guess. I haven't come across this term (free basis) in my reading of any standard textbook on Linear Algebra (cf Hoffman/Kunze).

6. May 10, 2007

### pivoxa15

I am talking about it in the sense of modules.

7. May 11, 2007

### quasar987

If you look here

http://en.wikipedia.org/wiki/Free_module

they define a free module as a module having a free basis. But then they give the definition of a free basis and it is an exact analogy to what is simply called a 'basis' in linear algebra:

http://en.wikipedia.org/wiki/Basis_(linear_algebra)#Definition

Another reason why I suspect that there is no difference btw the two is the following sentence in the article about modules:

"However, modules can be quite a bit more complicated than vector spaces; for instance, not all modules have a basis, and even those that do, free modules,[...] "

Last edited: May 11, 2007
8. May 11, 2007

### matt grime

Vector spaces are modules for fields. All modules for fields are free, so in this case the two notions agree.