could

All forms give the speaker's view of possibility or impossibility,
but there is often a crossover in the emphasis on Time, Hypothesis or Relationship,
as shown in the diagram below...
...as always, the situation is most important.

Remote forms:

	Time	Hypothesis	Relationship
	I could walk when I was 1 year old (general ability only, specific one-time actions are usually made with " w__ able to...")	She could be late home tonight	I could help you...
	I couldn't help her	She couldn't still be at work	You could not be more helpful
	Could you understand that message?	Could she be in her car?	Could you help me please?
N.B.	She could have stopped for a rest ( ...it was allowed)	She could have stopped for a rest (...I think she did that)