Altogether means completely, entirely, or all things considered. It refers to things as a whole.
- Altogether, this year has been difficult for everyone due to the global pandemic.
- At my dad’s funeral, it’s altogether acceptable to hug me. I’ll need it.
All together can be used when referring to everyone or everything together.
- It’s time to sing. All together at the same time, now!
- For a team building experience, we went all together to the Diefenbunker Cold War Museum for a scavenger hunt.