It's called the "Shade Leaf"
the base is the place where the leaf joins its stem
an oak tree leaf duuh
leaf scar
While the entomology of leaf is not known for certain, it is possible it has to do with a leaf on a tree. Since a leaf is an extension of a tree, a table leaf is an extension of a table.
Needles
you parked near a tree and your window was open
Because its leaves represent peace olive branch is the peace leaf
The single-leaf Pinyon tree is Nevada's state tree.
scar
Maple leaves.
Trees "breathe" CO2 (carbon dioxide) through extremely small openings between the plants cells on the bottom of the leaf, called stomata (stoma singular). Through the same stomata O2 leaves the leaf.
Broad"leaf`\, n. (Bot.) A tree (Terminalia latifolia) of Jamaica, the wood of which is used for boards, scantling, shingles, etc; -- sometimes called the almond tree, from the shape of its fruit.