Vulnerable and susceptible are related, but they are not perfect synonyms.
Vulnerable means open to harm, attack, or emotional hurt. It often describes a weak position or lack of protection. A person, group, or system can be vulnerable.
Susceptible means likely to be affected by something. It is often used for illness, influence, persuasion, or change. The focus is less on being exposed and more on being easily affected.
- Vulnerable: After the scandal, he felt vulnerable.
- Susceptible: Children are more susceptible to colds in winter.
A good way to remember the difference is this: vulnerable highlights risk or weakness, while susceptible highlights responsiveness or tendency.
Sometimes both can fit, but the meaning shifts slightly. A computer system can be vulnerable to attack because it is unprotected. A person can be susceptible to misinformation because they are easily influenced. Choosing the right word makes your meaning more precise.