Formal:
* Commence: implies a formal or official start.
* Initiate: suggests a deliberate act of starting something.
* Embark: implies starting a journey or undertaking.
* Inaugurate: suggests a formal beginning of something new.
* Enter upon: implies a more formal way of starting something.
Informal:
* Start: a general and simple word.
* Launch: implies a forceful or energetic beginning.
* Kick off: implies a lively and exciting start.
* Get going: implies action and movement.
* Hit the ground running: implies a fast and energetic start.
Other options:
* Resume: implies starting something again after an interruption.
* Proceed: implies continuing something that has already begun.
* Set out: implies starting a journey or task with a specific goal in mind.
* Take up: implies starting something new as a hobby or interest.
* Undertake: implies starting a serious or difficult task.
The best word to use will depend on the specific context and the tone you want to convey.