What is meant by deactivating groups? Explain with suitable examples.

(N/A) Definition: Groups that,when attached to a benzene ring,make the subsequent electrophilic aromatic substitution reaction slower than that of benzene are known as deactivating groups.
Examples: Most meta-directing groups are deactivating groups,such as $-COOH$,$-NO_2$,$-SO_3H$,$-COCl$,$-COR$,$-COOR$,and $-CN$.
Explanation:
$(a)$ Resonance effect: In meta-directing groups,the $\pi$-electron density of the benzene ring is delocalized towards the substituent group due to resonance. This reduces the electron density within the ring,making it less susceptible to electrophilic attack.
$(b)$ Inductive effect: Most of these groups exert a strong electron-withdrawing inductive effect ($-I$ effect),which pulls electron density away from the ring,further decreasing the electron density and thus deactivating the ring towards electrophilic substitution.