The verb's aspect refers to the frequency or the duration of an action. This information is grammatically marked in a number of languages. Languages often make a basic distinction between complete one-time actions (called "perfective" from Latin perfectum 'done through' or 'carried out'), and ongoing or incomplete actions (labeled "imperfective"). Other aspects include the "progressive" (for actions in progress at a given time, like was studying) or the "frequentative" (actions done over and again like keep studying). Crucially, pay attention to the difference between aspect and tense.