Why is boric acid considered as a weak acid?

(N/A) Boric acid $(H_3BO_3)$ is considered a weak acid because it does not act as a proton donor $(H^+)$ by itself. Instead,it acts as a Lewis acid by accepting a lone pair of electrons from the $OH^-$ ion of a water molecule to complete its octet. The reaction is: $B(OH)_3 + 2H_2O \rightleftharpoons [B(OH)_4]^- + H_3O^+$. The release of $H^+$ ions is a result of this interaction with water,making it a weak monobasic Lewis acid.