toska (ˈtō-skə); noun

russian - at its deepest and most painful, it is a sensation of great spiritual anguish, often without any specific cause. at less morbid levels it is a dull ache of the soul, a longing with nothing to long for, a sick pining, a vague restlessness, mental throes, yearning. in particular cases it may be the desire of somebody or something specific, nostalgia, love-sickness. at the lowest level it grades into ennui, boredom.