Which of these necessarily means directly under in such a way that a vertical line can connect the two objects?
We do say 'below sea level', but not 'under sea level'.
Could one say 'The city was below the hills'?
Could one say: 'The city lay below the hills'?
Could one say: 'We were standing below the mountains'?
Could one say: 'Romeo was standing below Juliet's window'? (My feeling is that here we need 'under' because he is directly under it')
My theory is that when we say 'under' we mean that a vertical line can be drawn connecting the two things. Would you say that is correct?
When something is under something else, it is also below it, but the converse doesn't work. Is that correct?
How about 'beneath' and 'underneath'?