The Greek word for Just/Justify/Justification has basically the same meanings as the English word. When it is used by a court or judge it is “To declare someone is just”. “The judge declared that Joe was justified in killing the intruder”. In this case Joe was declare just by a higher authority. What he did was right and correct and lawful.
However it can also be used to present evidence of something. For instance. “Joe justified his stance on gun control with crime statistics.” In this case Joe was using crime statistics to show or prove his stance on gun control.
James 2:24 says You see that a person is justified by works and not by faith alone. …
The position taken by Protestants/Evangelicals is that justified in this context is evidential. In verse 18 it says Show me your faith apart from your works, and I will show you my faith by my works.
Both works (what we do) and our faith(what we believe and profess to believe) are evidences that we are Children of God. If we profess faith alone, without works, then we don’t have any evidence that our faith is a real saving faith that has brought forth a change in our hearts and life by the work of the Holy Spirit in our life. James is imploring us to not be made right by our works but to “Show you my faith by my works”. The implication in Verse 14 What good is it, my brothers, if someone says he has faith but does not have works? Can that faith save him? is that there is a faith that cannot save. What kind of faith doesn’t save? An intellectual faith and a dead/useless faith. Those are kinds of faith but they aren’t the kind of faith that changes a person from death to life, from being an enemy of God to becoming a Child of God. So James is saying that if we have a true living(saving) faith then our works are evidence of that faith.
This concept is further affirmed and fleshed out in 1 John. Many places in the book talks about how if we don’t have love and obedience we are liars and not really children of God. But verse 3:10 says
By this it is evident who are the children of God, and who are the children of the devil: whoever does not practice righteousness is not of God, nor is the one who does not love his brother.
Practicing righteousness and loving our brother are evidence that we are children of God.