at the top of sth
prep. phr..prep. phr.. This means being at the highest point of something, or in the most important position.
prep. phr.. Indicates the highest physical point of an object or location, or the most senior position within a hierarchy.
The bird is at the top of the tree.
After years of hard work, she is finally at the top of her field.
At the top of the agenda for the international summit was the urgent matter of climate change, overshadowing all other discussions.
This phrase can refer to a physical location (top of a hill) or a metaphorical rank (top of the class).
Contrast with 'on top of', which implies placement on a surface, whereas 'at the top of' refers to a point or rank.
She is on the top of her class.She is at the top of her class.Use 'at' for a position within a group or hierarchy; 'on' is typically for a physical surface.