John Keats' poem 'Foster-Child of Silence and Slow Time' is a reflection on the passing of time and the inevitability of death. The poem is written in an URN-shaped form, with the first and last lines being the same. The term 'foster-child' refers to the idea that time is like a parent, and we are its children. The poem speaks of how time passes slowly, and how silence is a part of life. Keats' use of the URN as a metaphor for time is a reminder of the permanence of death and the transience of life.