What is the difference between spies and detectives?

SPY:

A person who secretly collects and reports information on the activities, movements, and plans of an enemy or competitor.
Synonyms:  secret agent, special agent


In real life, espionage isn't much like what you see in the movies.  Still, spying is a useful and dangerous way for governments to gather secret information from their enemies.

­World leaders are faced with making important decisions every day, and information is the key to making the right decision. How many troops does your enemy have? How far are they in developing their secret weapons?

While some of this information (known as intelligence) may be readily available, most countries keep information that could be used against them secret. Of course, this secret information is often the most valuable. To gain access to secret information, governments use espionage, a blend of subterfuge, deception, technology and data analysis. Espionage can also be used to sabotage the enemy by supplying them with incorrect information.

DETECTIVE:

A person, especially a police officer, whose occupation is to investigate and solve crimes.
Synonyms:  investigator, private investigator (private i)


Private detectives and investigators provide private investigative services to collect information. Private detectives analyze information to solve mysteries and uncover facts. They assist during criminal and civil cases, insurance fraud, missing persons investigations, and child protection and custody disputes.  Private detectives utilize many investigative methods. They generally use computers to find documents, locate deleted emails, and conduct database searches. Investigators utilize computers to find information about criminal records, telephone numbers, court judgments, and motor vehicle registration.