Security (noun)

1. The state of being free from danger or injury.
2. Measures taken by a government, organization, or individual to guard against espionage, sabotage, attack, or other threats.
3. A thing that secures, such as a lock or lock-and-key mechanism, or the condition of being secured.
4. A stock, bond, or other form of financial investment that provides a return in the form of fixed payments and the appreciation of the security's value.
5. An assurance, guarantee, or pledge of protection or safety.

Origin:

Late middle english: from old french securite, from latin securitas, from securus 'safe'. the original sense was 'freedom from care or disturbance', later 'freedom from danger or harm', and later still 'safety or protection' (sense 2).

Examples:

1. The airport has increased security measures to prevent terrorist attacks.
2. He hired a bodyguard for personal security.
3. The security measures at the bank made him feel safe.
4. The company issued a new security to raise funds for expansion.
5. The home alarm system provides a sense of security for the family.