1) Therefore used as as a result of something that has just been mentioned: Their car was bigger and therefore more comfortable.
2) Hence - for this reason: The cost of transport is a major expense for an industry. Hence factory location is an important consideration.
3) Consequently - as a result: Most computer users have never received any formal keyboard training. Consequently, their keyboard skills are inefficient.
4) Accordingly - in a way that is suitable for a particular situation or that is based on what someone has done or said: Katherine still considered him a child and treated him accordingly.
Finally, first three words are very similar and have the same meanings.