The term has many meanings. It translates 13 Hebrew and 3 Greek words.
In a political sense, a ruler was one who controlled a state (2 Chronicles 7:18; Psalm 105:20; Proverbs 23:1; 28:15; Ecclesiastes 10:4; Isaiah 14:5; 16:1; 49:7; Jeremiah 33:26; 51:46; Micah 5:2), or a state that controlled a people (Judges 15:11). The usual term for ruler was "king." But, many in Israel preferred the Hebrew term translated as "leader," meaning "one placed in front." This was due to the king's unpleasant associations. For example, Samuel rejected the former term but used the latter (1 Samuel 9:16; 10:1; 13:14; 25:30; 2 Samuel 5:2; 6:21; 7:8). Other Hebrew words are translated “ruler” in the King James Version. However, most modern translations prefer alternatives to this more generic term.
In the New Testament, the Greek word for “ruler” refers to administrative or religious leaders (see Matthew 9:18, 23; Luke 8:41; 18:18; 23:35; 24:20; John 3:1; 7:26, 48; 12:31; Acts 3:17; 4:5, 26; 7:27, 35; 13:27; 14:5; 16:19; 23:5; Romans 13:3). Ephesians 6:12 mentions the rulers of the darkness of this world.