Loneliness

Loneliness,how should we define it properly? Actually,there is no certain or even most appropriate sentence to tell what exactly it's. For me,It's a state of being lonely that must experienced in our life cycle stage. Although,it's an crucial test but we still need to cross over it no matter how,it'll still there for us.
What can I say is always remember to cherish,value,treasure the moment and the screen that was appearing during your lifetime. Sometime,things may not happen twice as before.