Correct spelling, explanation: defense and defence have the same meaning and serve as alternative spellings of the same word. The difference lies in their spelling conventions based on regional variations of English. Both words ultimately trace back to the same Latin root, defensum, but the spelling conventions diverged over time as English evolved on either side of the Atlantic. Defense is more commonly used in American English and defence – in British English.

Definition of defense:
Noun, the action of defending from or resisting attack
The team’s strong defense prevented the opposing players from scoring any goals during the match.
The cybersecurity team implemented robust defense measures to safeguard the company’s sensitive data from cyber threats.

Collocations with defense:
Some most commonly used collocations include:
1. Self-defense: the act of protecting oneself from physical harm.
She took self-defense classes to learn how to protect herself in case of an emergency.
2. Defense strategy: a plan or approach designed to protect against potential threats or challenges.
The military developed a comprehensive defense strategy to safeguard the country’s borders.
3. Defense contractor: a company that provides goods or services related to military and defense technology.
The government awarded the contract to a defense contractor for the production of advanced weaponry.
4. Defense against: protection or resistance against a specific threat or danger.
Vaccination is a crucial defense against certain infectious diseases.

Correct spelling, explanation: the choice between defence and defense depends on the variety of English you are using. Use the first one if you are writing in British English or another variety of English that follows British spelling conventions and the second one if you are writing in American English. If there are no specific guidelines, you can choose the spelling – defence or defense – based on your own preference or the variety of English you are most comfortable with. Consistency in spelling is important in writing.