Modal Logic Question

I seem to have forgotten all the logic that I’ve been studying.
Some formal definitions (I know of). For some proposition p

  1. p is necessarily true: The negation of p entails a contradiction
  2. p is possibly true: p doesn’t entail p contradiction

Perhaps we can extend these simple notions to nonpropositions such as wood and pumpkins:

  1. x is necessary: the absence of x would entail a contradiction
  2. x is possible: the presence of x doesn’t entail a contradiction