In the NT, this word usually refers to Jesus as the only son of God. There are three passages in Luke, however, where it refers to other people’s only children:
• The widow of Nain’s son: As he drew near to the gate of the town, behold, a man who had died was being carried out, the only son of his mother, and she was a widow, and a considerable crowd from the town was with her (Luke 7:12)
• The ruler of the synagogue’s daughter: For he had an only daughter, about twelve years of age, and she was dying (Luke 8:42)
• The healing of a boy with a demon: And behold, a man from the crowd cried out, “Teacher, I beg you to look at my son, for he is my only child” (Luke 9:38)
In the Greek OT, the Septuagint, the meaning is more fluid. Here the word can sometimes have the more general sense of solitary or alone, for example:
• Turn to me and have mercy, for I am alone and in deep distress (Psalm 25:16)
But there are also passages where the Septuagint translators are already using the word monogenes in its NT sense:
• Then Jephthah came to his home at Mizpah. And behold, his daughter came out to meet him with tambourines and with dances. She was his only child; besides her he had neither son nor daughter (Judg 11:34).