Pseudohalides are 'fake halides'. Their chemistry involves resemblence with true halides $\left( F ^{-}, Cl ^{-}, Br ^{-}, I ^{-}\right) \cdot CN ^{\ominus}$ is a pseudohalide. It has
similar properties to those of halogens. Pseudohalide is any uni-negative species composed of two or more atoms, which in the free state shows certain characteristics of the halogens,
e.g. these combine with hydrogen to form an acid and with silver to form a salt insoluble in water.