Syntax ·入terms or入expressions: (Terms)M,N :x x.M MN Lambda abstraction(Ax.M):"anonymous"functions intf(intx){return x;}→入x.x Lambda application (M N): int f (int x){return x;} f3: →(x.x)3=3Syntax •  terms or  expressions: (Terms) M, N ::= x | x. M | M N • Lambda abstraction (x.M): “anonymous” functions int f (int x) { return x; } ➔ x. x • Lambda application (M N): int f (int x) { return x; } f(3); ➔ (x. x) 3 = 3