Let L be a non empty relational structure. Note that every map from L into L which is closure is also projection. Let L be a non empty reflexive relational structure. One can check that there exists a map from L into L which is closure. Let L be a non empty reflexive relational structure.
L is closure.
Let L be a non empty relational structure and let k be a map from L into L . Let L be a non empty relational structure. Observe that every map from L into L which is kernel is also projection. Let L be a non empty reflexive relational structure. One can verify that there exists a map from L into L which is kernel.