When a cell is in a solution where the concentration of solute is the same in the cell as in the solution, the solution is called?

The answer to this question would be: isotonic

An isotonic solution has a same tonicity/concentration to the cell. This kind of solution will not cause osmosis to occur so it wouldn't shrink or swell the cells. This is why an isotonic solution is safer for the cells. The normal saline solution is isotonic to human cells and used frequently in medicine to replace body fluid.