# What does it mean if a solution is concentrated?

For instance, $\text{3 M HCl}$ is not considered concentrated for laboratory purposes, but we tend to see $\text{12.06 M}$ (37% $\text{w/w}$) $\text{HCl}$ considered concentrated, "reagent-grade" $\text{HCl}$.
Or, ${\text{1 M H"_2"SO}}_{4}$ is not considered concentrated, but we tend to consider $\text{18 M}$ (~~98% $\text{w/w}$) ${\text{H"_2"SO}}_{4}$ concentrated.