in my profession, brevity is key. the frequent use of abbreviation in source code serves two purposes: 1) it makes typing easier; 2) it helps us fit more into a smaller visual space, emphasizing structure over fine detail. this is why vowels are often dropped: wrds cn b rckgnzed wth vry few ltrs. yet the most important variable, the most common, is i: the name i is short for the latin iterum, meaning again. generally, i is not bound to a single value but many in succession -- 1 2 3 and so on. i is a number; a stage of processing, an index into a population. its principal purpose is to represent something else. it may stand for anything, and everything. it counts, but does not count. recently, in some languages, i's ubiquity has been challenged by a variable which represents "the thing currently being manipulated". this thing is often called this or, self. the use of this is so crucial in these languages that often the variable can be eliminated entirely, abbreviated into nothingness -- this (we say) is implicit. this is understood. so when reading these texts, you must always keep in mind who is speaking at the moment: because lurking behind every verb and object is the invisible unwritten subject, the self. this is understood.