In 2 Kings 20:5; Psalms 6:6; 39:12; 80:5, tears signify internal sadness or gladness. (Arcana Coelestia 4215[2], 7251)

In Lamentations 2:11, a tear signifies grief on account of truth destroyed. (Arcana Coelestia 10031[2])

In Revelation 7:17, it signifies that they shall no longer combat against evils and falsities, and so shall not grieve, but be in goods and truths, and thus heavenly joys. (Apocalypse Revealed 385, Apocalypse Explained 484)

'A tear' signifies grief because of a lack of understanding of truth.