Carboxylic acids contain a carbonyl group but do not show the nucleophilic addition reaction like aldehydes or ketones. Why?

(N/A) The carbonyl carbon in carboxylic acids is less electrophilic than in aldehydes and ketones. This is due to the resonance effect of the $-OH$ group,where the lone pair of electrons on the oxygen atom is delocalized into the carbonyl group.
This resonance structure,as shown below,reduces the partial positive charge on the carbonyl carbon:
$-C(=O)-OH \leftrightarrow -C(-O^-)=O^+-H$
Because the electrophilicity of the carbonyl carbon is significantly reduced,it does not readily undergo nucleophilic addition reactions.