a tear: the drop that falls from a weeping eye, and so, in the plural, weeping made visible.
This is the concrete word for a tear. Greek had other words for the sound grief makes (κλαυθμός) and for grief as a settled condition (πένθος), and a verb for the act of shedding tears (δακρύω). This word names the drops themselves, the part of sorrow you can see on someone's face. In the New Testament it is almost always plural, so English renders it "tears" nearly every time.
One small word stretches across very different scenes because tears are the plainest evidence of what a person actually feels. Writers reach for them when words on their own would sound thin. Paul does not simply say he warned the leaders at Ephesus; he says he did it "with tears" for three years, and that is what makes the warning land. Hebrews does not simply say Jesus prayed; it says he prayed with loud crying and tears.
Because a tear is small and countable, it can also stand for the whole of human sorrow. When Revelation promises that God will wipe away "every tear from their eyes," it picks up a picture from Isaiah: not one drop is overlooked, and the gesture is as personal as a hand on a child's face.
What the word never does is drift away from real weeping. Whether it is a woman wetting Jesus's feet, the tears Paul remembers on Timothy's face, or Esau crying too late, they are always actual tears.