a leaf is a part of a tree & an oak is a kind of tree & shape of the parts of something is a property of that something ->  the shape of oak trees leaves is a property of oak trees  a maple tree is a kind of tree & a leaf is a part of a tree & shape of the parts of something is a property of that something ->  the shape of maple trees leaves is a property of maple trees  the shape of oak trees leaves is a property of oak trees & the shape of maple trees leaves is a property of maple trees & trees of different species have differently shaped leaves ->  oak trees and maple trees have leaves of different shapes properties  oak trees and maple trees have leaves of different shapes properties & classifying means grouping objects / materials by their properties ->  oak trees and maple trees can be classified by the shape of their leaves  oak trees and maple trees can be classified by the shape of their leaves & classifying is similar to telling the difference -> we can tell the difference of oak trees and maple trees by the shape of their leaves