What does $∆\mathrm{H}$ represent in

$\mathrm{X}\left(\mathrm{g}\right)+{\mathrm{e}}^{-}\stackrel{ }{\to }{\mathrm{X}}^{-}\left(\mathrm{g}\right); ∆\mathrm{H}=-\mathrm{x}$

The amount of energy released due to addition of an electron into valence shell of an atom in it's gaseous state is known as electron gain enthalphy