The difference between altogether and all together
TLDR: Altogether means including everything, whereas all together means ‘all in once place or time’.
Altogether and all together do not mean the same thing!
altogether (adverb)—entirely, completely; including everything or everyone; on the whole
Garrus was altogether too tired to accompany Commander Shepard on the next mission. (Must be all the calibrating!)
Altogether, Simon had two rubbers, six pencils, five pens, a calculator and a permanent marker in his pencil case.
‘I think, altogether, I had a very pleasant evening.’
All together, however, is a phrase which means ‘all in one place’ or ‘all at the same time’. For example:
I neatly stacked my books all together in the middle of the room.
The team walked out onto the pitch all together.
Note that the phrase all together can be split up.
I stacked all my books together in the middle of the room.
The team all walked out onto the pitch together.
Just like with already and all ready, if you can remove the all from the sentence without damaging the meaning, then all together is the correct phrase to use. Such as; ‘The team walked out onto the pitch together’. If your sentence ends up sounding something like this, though, ‘Garrus was together too tired to accompany Commander Shepard on the next mission’, which makes no sense, then altogether is the correct term to use.
Good luck! (And let’s hope Garrus perks up in time to save Earth!)