the state of being vulnerable or exposed
"his vulnerability to litigation"
"his exposure to ridicule"
susceptibility to injury or attack
"The castle's high walls provided excellent defense, but its narrow gate remained a vulnerability that enemies could exploit."
Susceptibility to attack or injury; the state or condition of being weak or poorly defended.
"The old wall showed a clear vulnerability where the mortar had crumbled, leaving the gate exposed to enemy fire."
In plain English: Vulnerability is when you are open to being hurt because your defenses aren't strong enough yet.
"The hacker exploited a software vulnerability to gain access to millions of user accounts."
Usage: Use vulnerability to describe an inherent weakness that makes someone or something susceptible to harm, rather than a temporary feeling of sadness. It often refers specifically to security flaws in systems or emotional points where a person can be easily hurt by criticism.
The word vulnerability comes from the Latin root vulnerable, meaning "able to be wounded," combined with the suffix -ity to indicate a state or condition. It entered English as an abstract noun describing the quality of being susceptible to harm, building directly on the existing adjective vulnerable.