Final answer:
In chemistry, [C] usually stands for the concentration of a substance within a given volume of solution, and is a key concept in understanding reaction rates and equilibrium.
Step-by-step explanation:
The symbol [C] in chemistry typically stands for concentration. Concentration refers to the amount of a substance in a specified volume of solution and is commonly expressed in terms of molarity, which is moles of solute per liter of solution (mol/L). It is an essential concept in chemistry, particularly in the context of reaction rates and equilibrium.