Disconjugacy of solutions of linear differential equations

It is an expository article devoted to the disconjugacy theory for decisions of the homogeneous differential equation of $n$-th order. We give new proofs of some basic results of this theory, such as sufficient conditions for disconjugacy, some implications from disconjugacy, properties of disconjugate equations. We also give new sufficient conditions of disconjugacy for second order differential equations.