text: Things are said to be named 'equivocally' when, though they have
  a common name, the definition corresponding with the name differs
  for each. Thus, a real man and a figure in a picture can both lay
  claim to the name 'animal'; yet these are equivocally so named,
  for, though they have a common name, the definition corresponding
  with the name differs for each. For should any one define in what
  sense each is an animal, his definition in the one case will be
  appropriate to that case only.
  On the other hand, things are said to be named 'univocally' which
  have both the name and the definition answering to the name in
  common. A man and an ox are both 'animal', and these are
  univocally so named, inasmuch as not only the name, but also the
  definition, is the same in both cases: for if a man should state
  in what sense each is an animal, the statement in the one case
  would be identical with that in the other.
  Things are said to be named 'derivatively', which derive their
  name from some other name, but differ from it in termination.
  Thus the grammarian derives his name from the word 'grammar', and
  the courageous man from the word 'courage'.