If someone is not mindful of your personal space and you want them to give you space, you could say "Please step back" or "Step back, please." **depending on your tone, it can be interpreted as a peaceful request or rude. -"Back off" is typically interpreted as rude and is used when in heated discussion with disregard to personal space. -"Back up" can be interpreted as rude, but you could also say "Please back up" or "Back up, please" to make it a polite request. **Tone is most important.** I hope this helps you!

Backup- used when you need someone to support you. Example - Olivia, could you BACKUP me in the report today? back off- used when you want to someone to go away from you (used in informal) Example - Just BACK OFF and let us do this on our own, will you? Step back - used to widthraw from a situation Example - I think that it is important to STEP BACK and see it from a different point of view when you are considering what to do.