How can you determine whether a solution is dilute or concentrated given its concentration? I don't whether this is a stupid question or not but I couldn't find any answer.
There is no hard and fast definition of "concentrated" or dilute. For example, concentrated HCl generally refers to a 12 mol/L solution of HCl. Concentrated sulfuric acid is 18 mol/L. When we refer to a "concentrated" solution, we are generally referring to the most concentrated solution that you can prepare, or that you can buy from a supplied. https://www.sigmaaldrich.com/chemistry/stockroom-reagents/learning-center/technical-library/reagent-concentrations.html