1. ‘Thus’ means ‘in this/that way’ – it relates to ‘HOW’ – the manner in which – this or that happens or comes about. It has a practical flavor.
Traditionally, you arrange things thus. = Traditionally, this is how you arrange things.
2 .’Therefore’ means ‘for this reason’, or ‘because of this or that’ – it relates to deductive reasoning, it tells WHY this or that is so, or happened.
He was late and therefore missed the bus. = he was late and for this reason missed the bus.
3. ‘Hence’ means ‘from this/that’ – it relates to WHERE – position, or point in time; it tells from where or what, or to where or what, something comes, derives, or goes.
i. Get thee hence! = Get yourself away from here!
ii. Henceforth all entrances will be guarded. = From now on all entrances will be guarded.
iii. She got the job – hence her good spirits. = She got the job and her good spirits derive from that fact. (Note the different slant to ‘therefore’, which would also fit, but would say ” her good spirits are due to (’because of’; ‘for that reason’) that”.