What do the terms epiphany, theme, and symbol mean in the context of "Tears, Idle Tears" by Elizabeth Bowen?

Literary critical terms such as theme, symbol, and epiphany are not unique to this story, but give you the tools to describe and understand narratives. A theme is a broad issue, concern, or point addressed by a literary work. In this case, the theme is signaled by its appropriating a line from Tennyson as a title. That Tennyson line refers to Virgil's lacrimae rerum (tears of things), a notion of an overwhelming sense of sadness not connected with personal emotion (i.e. not melancholia or depression nor triggered by a specific event), but with a sense of sorrow at the heart of life. An epiphany is a moment of realization, in this story perhaps applicable to the woman as well as Frederick. In the case of symbols, you might think of how George and Frederick act as symbols of sorrow and the ducks as simple pleasures.