The term 'strength of a solution' is used to describe the concentration of a solution, which is usually measured in terms of molarity or moles per liter. The two crossword solutions for this term are 'titer' and 'titre', both of which have five letters. Titer is a term used in chemistry and biology to describe the concentration of a solution, while titre is a French word with the same meaning. Both terms refer to the amount of solute present in a given volume of solution.