normality
/ nor-MAL-ih-tee /
Some acids hand out one proton; sulfuric acid can hand out two. If you only counted molecules, the double-handed one would look weaker than it really is in a titration. Normality fixes this by counting the reactive units rather than the whole molecules.
Normality (unit equivalents per litre, written N) is the number of equivalents of solute per litre of solution. An 'equivalent' is one reactive unit — one proton for an acid, one electron for a redox reagent — so normality already builds the stoichiometry into the number.
It was once standard in titration work because it lets you say 'equal volumes of equal normality react completely', skipping the balancing step. Modern practice prefers molarity, since normality depends on which reaction you have in mind and the same bottle can have different normalities in different contexts.
A 1 mol/L solution of sulfuric acid is 2 N for acid-base purposes, because each molecule can donate two protons, so one litre supplies two equivalents.
Molarity counts molecules; normality counts reactive units.
Normality is no longer recommended by IUPAC precisely because it is ambiguous without naming the reaction. If you quote N, also say whether it is for acid-base or redox use.