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.
Span is the amount of area or the amount of time that something encompasses. 1  An example of span is how long you live. 2  An example of span is a house on three acres.  a unit of linear measure equal to nine inches: originally based on the distance between the tips of a man's extended thumb and little finger.