By one's self; apart from, or exclusive of, others; solo.
"alone" is a perfectly correct and usable word in written English. You can use it as an adjective to describe something or someone, as an adverb to describe an action or as a noun when referring to someone who is by themselves. For example: "She felt so alone in the big city.".
She is not alone.
But it is not alone.
If I could save the Union without freeing any slave I would do it, and if I could save it by freeing all the slaves I would do it; and if I could save it by freeing some and leaving others alone, I would also do that.
"Let us assure you that the Government will do all we can to defeat the voices of division, but ultimately the challenges of integration and radicalisation cannot be solved from Whitehall alone.
PH: "Leave me alone, you have no place in my life and no right to be proud.
They were not alone.
And it is not alone.
Since I tried Ludwig back in 2017, I have been constantly using it in both editing and translation. Ever since, I suggest it to my translators at ProSciEditing.
Justyna Jupowicz-Kozak
CEO of Professional Science Editing for Scientists @ prosciediting.com