Analogues are drugs that have close structural resemblance and similar effects. For instance one could argue that naproxen (Aleve) is an analog of ibuprofen (Motrin/Advil). Most analogues are designed because true synthetic natural products are hard to make, or are not potent enough.
Definition of several. 1a : separate or distinct from one another federal union of the several statesb (1) : individually owned or controlled : exclusive a several fishery â compare common (2) : of or relating separately to each individual involved a several judgmentc : being separate and distinctive : respective specialists in their several fields.
Vector: a quantity with more than one element (more than one piece of information). That isn't the best definition, but it is better than magnitude and direction.. Perhaps the best way to understand vectors is to look at some examples.