We all experience them from time to time but don't necessary like them: the changes in circumstances over which we have no control, handily summed up by the plural of this word, vicissitudes. Its main root is a Latin word for "turn." One thing that doesn't change is its spelling, so it pays to note the single c and double ss. This also gives you a jump on the delightfully erudite related adjective, vicissitudinous.