Tsedek means righteousness, justice, what is right, or vindication. It appears about 120 times. It describes rightness in legal, ethical, and relational contexts. God's tsedek is His perfect justice and saving righteousness.
Tsedek in the prophets often means God's saving justice — His commitment to set things right. The Messiah is called 'The LORD Our Righteousness' (Jeremiah 23:6). Righteousness and justice are the foundation of God's throne (Psalm 89:14). Paul's 'righteousness of God' (Romans 1:17) stands in this tradition.