Black willow has long and slender "lanceolate" leaves.
Water oak leaves are "spatulate", with slender bases and very broad tips.
Redbud leaves are heart-shaped or "cordate".
Silver maple (and most other maples) are round in outline or "orbicular".
Zelkova leaves are ovate (egg-shaped) and broadest near the base.
Spicebush leaves are elliptical. An ellipse is symmetrical.
The leaflets of buckeye leaves are obovate (egg-shaped and broadest near the tip).
Chinese chestnut leaves are oblong. They have an elongated oval shape.