What is the significance of the terms

What is the significance of the terms - ‘isolated gaseous atom’ and ‘ground state’ while, defining the ionisation enthalpy and electron gain enthalpy?

Ionisation enthalpy It is the minimum amount of energy required to remove an electron from an isolated gaseous atom (X) in its ground state.
X -------> ${{X}^{+}}$ + ${{e}^{-}}$
The force by which an electron is attracted by nucleus is also affected by the presence of other atoms within its molecule or in the neighbourhood. Therefore, ionisation enthalpy is determined in gaseous state because in gaseous state interatomic distances are larger and interatomic forces of attractions are minimum. Further more, ionisation enthalpy is determined at a low pressure because it is not possible to isolate a single atom but interatomic attractions can be further reduced by reducing pressure. Due to these reasons, the term isolated gaseous atom in ground state has been included in definition of ionisation enthalpy.
Electron gain enthalpy :It is the energy released when an isolated gaseous atom (X) in ground state gains an electron v to form gaseous anion.
X + ${{e}^{-}}$ -------> ${{X}^{-}}$
The most stable state of an atom is ground state. If isolated gaseous atom is in excited state, comparatively lesser energy will be released on addition of an electron. So, electron gain enthalpies of gaseous atoms must be determined in their ground states. Therefore, the terms ground state and isolated gaseous atom (explained above) has been also included in the definition of electron gain enthalpy.