A crime is a well-known word and this word and everybody knows this word but it is very difficult to define crime. 

The crimes evolved with the evolution of this word. Earlier there were only murders, theft but nowadays there were cases of NI act, cybercrime. 
Crime is an essentially contested concept. There is no universally agreed definition of what a crime is.
For the purposes of data collection and comparison, crime data is usually divided into two broad categories: personal crimes and property crimes. Personal crimes include crimes of violence such as murder and robbery as well as any other criminal offenses that involve direct contact between a perpetrator and a victim, such as rape, aggravated assault, and battery. Property crimes are those in which personal property is the object of the offense and there is no force or threat of force used against the person to whom the property rightfully belongs.

Elements of Crime 

There are some elements that make any act as a crime. It is clear from this that the elements which make the act as crime are different. 
Criminologist Hall has explained seven elements of the crime. 

(a) Doing any criminal act intentionally and carelessly. 
(b) Doing such act with malafide intention or criminal intention. 
(c) Establishment of the link between malafide intention and conduct. 
(d) Such act causing damage to anyone 
(e) Prohibition of such damage by law 
(f) When there is a causal relation between voluntary conduct and damage prohibited by law 
(g) The existence of punishment as specified by law for such acts 

The following are four basic elements of the crime:

1.    Accused person

The first element requires that the wrongful act must be committed by a human being. In ancient times, when criminal law was largely dominated by the idea of retribution, punishments were inflicted on animals also for the injury caused by them, for example, a pig was burnt in Paris for having devoured a child, a horse was killed for having kicked a man. But now, if an animal causes an injury we hold not the animal liable but its owner liable for such injury.

2.    Mens rea

Mens Rea is the most important element to prove a crime has taken place. It means it was the intention of the wrongdoer to purposely/knowing/willing and with proper planning to cause harm to a person, animal or property. 

The element of mens rea itself comprises of certain inherent elements. These include intention, motive or knowledge. Which of these elements must exist in order to constitute an offense generally depends on the relevant provision.

3.    Actus reus

It is the guilty Act that follows guilty intention. An act will only be called a crime if both elements are present. The guilty intention of person leads them to act in accordance to it and hence it turns into a crime.

4.    Injury

 For a particular crime to take place it necessary for the injury to occur. After having a guilty mind and doing the guilty act if the injury does not occur then that crime is not considered as committed.