# General question: Vix or Vxi?

I have a very general question...

When labelling initial or final components on the x and y axes do you write, for example....

Vxi OR Vix

Is there a right or wrong answer? What is the convention?

fresh_42
Mentor
2021 Award
I have a very general question...

When labelling initial or final components on the x and y axes do you write, for example....

Vxi OR Vix

Is there a right or wrong answer? What is the convention?
Whatever ##V## stands for, the convention is either ##(v_x,v_y)## or ##(v_1,v_2)##. The former soon gets messy if higher dimensions come into play, which is why numbers as indices are preferred. If you have several points along the same dimension (axis), then some parameters would be nice: ##v_1(t_1),v_1(t_2),\ldots ## or ##(v_{11},v_{12},\ldots)##.

jtbell
Mentor
When labelling initial or final components on the x and y axes do you write, for example....

Vxi OR Vix

Is there a right or wrong answer? What is the convention?
Is this for an introductory physics course, where we deal with vectors for physical quantities in a rectangular 3-dimensional space (x,y,z directions)? Or is it for e.g. a linear algebra course where vectors are more abstract things, in an abstract space with an arbitrary number of dimensions?

If this is a physics context, I put the vector label or number first, followed by the component label, so vectors ##\vec v_i## (i = initial) and ##\vec v_f## (f = final) have components ##(v_{ix}, v_{iy}, v_{iz})## and ##(v_{fx}, v_{fy}, v_{fz})## respectively.

(Aha, now I see this is in the General Physics forum, so I suspect this is indeed a physics context. I originally came to this question via the "Unanswered Questions" section on the home page.)

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