# What does concatenation mean exactly in the context of machine learning?

In machine learning concatenation seems to have $$2$$ different meanings depending on the context.

For 2 tensors $$[a, b]$$ and $$[c,d]$$, concatenations of these $$2$$ tensors seems to mean either

$$[a,b,c,d]$$ or $$[a + c, b + d]$$

Which is the correct interpretation of the concatenation operation?

• The Wikipedia lemma on Concatenation is quite straight-forward refer to that. (I feel for you; when authors overload existing terminology things can quickly become misleading) May 28, 2017 at 22:15