Terminology Definition The order of a differential equation is the highest order deriva- tive that appears in the differential equation. Example (1)y+2xy=0: 4日10y4至，1无2000 Ordinary Differential EquationsTerminology Definition The order of a differential equation is the highest order deriva￾tive that appears in the differential equation. Example (1) y 0 +2xy = 0; (first order) (2) xy 00 +y 0 = x 2 ; (second order) (3) y 000 −x(y 0 ) 3 +y = 0; (third order) Ordinary Differential Equations