The strength of a fragrances is often determined by the concentration of aromatic chemicals to the solvent/carrier liquid. From weakest to strongest, here are the most commonly used terms.
Splash / Aftershave – Lowest concentration, often splashed on after shaving or bathing.
Eau de cologne (EdC) – Light fragrances, usually citrus-based that are often used to refresh during the summertime. Concentration is usually about 5%, but can range from 3-8%.
Eau de Toilette (EdT) – Usually about 10% concentration (range from 5-15%) of aromatic chemicals. Most fragrances marketed towards men are sold as EdT strength.
Eau de Parfum (EdP) – Usually about 15% concentration (range from 10-20%) of aromatic chemicals. These are stronger versions of fragrance that should last all day.
Perfume Extrait / Extract – The most concentrated version of a fragrance that is usually about 20% (range from 15-40%).
Attar – Pure perfume oil extracted from natural sources. Often used by people who are not allowed to use products that contain alcohol. One drop of an attar will warm up with body contact and last for a long time.
Things to note:
Different concentrations of the same fragrance might smell differently. The EdT might focus more on the top notes while the EdP will allow the full journey from the top to heart to base.