take up (v)
start (v)

Definition: begin work or acting in a certain capacity, office or job
Example: Take up a position. start a new job.

undertake (v)
contract (v)

Definition: enter into a contractual arrangement

tackle (v)
take on (v)
undertake (v)

Definition: accept as a challenge
Example: I'll tackle this difficult task.

start up (v)
start (v)
embark on (v)
commence (v)

Definition: get off the ground
Example: Who started this company?. We embarked on an exciting enterprise. I start my day with a good breakfast. We began the new semester. The afternoon session begins at 4 PM. The blood shed started when the partisans launched a surprise attack.

enter (v)
put down (v)
record (v)

Definition: make a record of

undertake (v)
set about (v)
attempt (v)

Definition: enter upon an activity or enterprise