a prophet: Jesus revealed knowledge about the woman that a stranger could not know (4:16–18; compare 1:48).
As the woman learned more about Jesus, what she called him showed her increasing understanding:
At first, she recognized him as "a Jew" (4:9) and called him "Sir" (4:11, 15, 19).
Later, she thought he might be "the Christ" (4:29), that is, the Messiah (God's chosen one).
Finally, the people of the village recognized him as "the Savior of the world" (4:42).
Her growing understanding of the identity of Jesus is a lesson for John’s audience (see 20:31).