The expression in the image consists of two terms: $B^i_j$ and $\delta^j_i$. Here's a breakdown of the symbols:

1. $B^i_j$: This is likely a component of a tensor. The superscript $i$ and the subscript $j$ indicate that it's a mixed tensor of rank 2, where $i$ is a contravariant index (upper) and $j$ is a covariant index (lower). Tensors like $B^i_j$ often appear in physics and differential geometry, especially when working with coordinate transformations.

2. $\delta^j_i$: This is the Kronecker delta symbol. It is equal to 1 when $i = j$ and 0 otherwise. The Kronecker delta is used in summations or matrix identities, often simplifying expressions involving tensors or matrices.

To give a clearer context, the combination of $B^i_j$ and $\delta^j_i$ might indicate a contraction or summation over the index $j$, resulting in a simpler expression depending on how the indices are set up.

Would you like more detailed examples on how tensors or Kronecker deltas work in various calculations?

Here are 5 related questions to consider:

1. How does tensor contraction work when combining $B^i_j$ and $\delta^j_i$?
2. Can you explain how the Kronecker delta simplifies tensor expressions?
3. What is the difference between covariant and contravariant indices in tensor notation?
4. How are mixed tensors used in the context of general relativity or differential geometry?
5. What role does the Einstein summation convention play in tensor algebra?

Tip: In tensor algebra, the Einstein summation convention is often used, where repeated indices (one upper and one lower) imply a summation over that index without explicitly writing the summation symbol.