TITLE: Is there a formal term for the placement of two symbols next to each other to imply an operation?
QUESTION [11 upvotes]: An example of what I am talking about is indicating multiplication by writing 
$$ab\equiv{a}\times{b},$$
in traditional real number algebra.
I was writing some notes involving matrix multiplication.  Previously in these notes I had specified that placing two tensor symbols next to each other indicates a direct product.  For example: 
Let $\mathfrak{A}=\left\{A_{ij}\right\}_{n\times{n}}$ and $\mathfrak{v}=\left\{v_{k}\right\}_{n\times{1}}.$   So in the context of my definition:
$$\mathfrak{A}\mathfrak{v}\equiv{\mathfrak{A}\otimes\mathfrak{v}}\equiv{\left\{A_{ij}v_{k}\right\}_{n\times{n}\times{n}}}.$$
But when working with matrices in linear algebra it is common practice to use
$$\mathfrak{A}\mathfrak{v}\equiv{\left\{\sum_k A_{ik}v_{k}\right\}_{n\times{1}}}.$$
Well, I want to use the latter definition in one example.  When I tried to state that placing the symbols next to each other without any operator symbol between them means matrix multiplication in this example, I found that I have no formal terminology for doing that.  I started to say "the juxtaposition of symbols...", but when I looked up the work juxtapose, I realized it's not what I mean.  It connotes an intent to compare and contrast. 
Is there a formal term for implying an operation by placing two symbols next to each other?

REPLY [2 votes]: I would write it as: "In this paper, direct product is used as the implicit operator for tensors ($\mathfrak{A}\mathfrak{v}\equiv{\mathfrak{A}\otimes\mathfrak{v}}$), while matrix multiplication is retained as the implicit operator for matrices and vectors."
However, using concatenation with unusual symbols carries risks. When I first saw $\mathfrak{A}\mathfrak{v}$, I thought it was a script W. It could also be interpreted as 21v in a strange script. Perhaps your audience is more familiar with this notation, but if you want your paper to be accessible to a more general audience, you should consider other choices for notation, such as explicitly writing the direct product operator, using symbols other than letters in Fraktur, or at least putting a space between them.