Apart means to be separated.
It's n not my problem if others don't know what apart means
Yes, your definition is just one of the ways that "apart" can be used in a sentence.
If we take another four-letter word, like "take" it has around 75 different contextual meanings, like, "take a seat" which can mean, "to sit" or to "carry," or "to take a trick" means "to win a trick" in a card game like Bridge or Five Hundred.
The expression that has been used in a post above in this form,
Apart from Christ, we are all the same.
What Marks states that when we live apart from the teaching of Christ, that we are all sinners. Another understanding is that "Apart from Christ there is no salvation, only sinners."
Both you and Marks have posted that each of you have a fundamental relationship with Christ that will lead to Eternal Life if each holds fast to Christ.
Your claim that "we cannot stand apart from Christ" is true because if we stand apart from Christ, we become sinners.
Marks claim that "Apart from Christ's {Salvation} we are all the same, {we remain sinners}," is also true.
From where I am observing this thread as an outsider, both of you are sinning by judging the other's salvation by your own respective standards, which means that you are both acting "God Like" and as such you both have deliberately turned away from God and because of this turning away to judge the validity of each other's salvation you both are sinning.
It is very easy to cross over the invisible line in the sand with respect to acting God Like. May God keep drawing both you and marks into His loving Embrace so that you both remain within His loving Embrace.
Shalom