Assay: a test system in which biological activity can be detected
Hit: a molecule with confirmed concentration-dependent activity in a screen, and known chemical structure. The output of most screens
Progressible hit: a representative of a compound series with activity via acceptable mechanism of action and some limited structure-activity relationship information
Lead: a compound with potential (as measured by potency, selectivity, physico-chemical properties, absence of toxicity or novelty) to progress to a full drug development programme
Pharmacophore: minimal structure with essential features for activity