The act of two people engaging in sexual intercourse, in which penetration occurs.
Primarily used for a man and woman engaging in sexual intercourse, for the purpose of reproduction, though the use has been co-opted to simply refer to penetrative sexual intercourse among two people.
In it's basest form, it means to have sex.
Purists will refer to it as a man penetrating a woman's vagina for procreation
This is based on the animal kingdom, in that animals will generally engage in copulation, when the female species is at in its most reproductive stage, meaning most fertile time.
They will differentiate between other forms, such as stating it was 'anal copulation' or 'oral copulation' with 'copulation' being the act of penetration.
Non Purists will simply refer to copulation as sex, where two people simply engage in penetrative actions, whether anal, oral, or otherwise.
From the Latin words 'copulare, copulat' which mean to join together, to be linked together.
In general terms, this is where the penis penetrates another person.
This can be anal penetration, or even in more broad terms, including oral penetration where the penis is inserted into another's mouth.
However, in a stricter context, it refers to the penis being inserted into a male's anus, or a female's vagina.
The most common term refers to male to female, vagina, though it can include a male to woman engaging in anal penetration.
Some form of lubrication is generally required, for anal copulation.
Practice (Associated Acts):
Copulation, the joining or union of two people, does require penetration by the penis.
Use of other methods, fall more under the general classification of 'penetrative sex'.
In instances where there is no penetration, it is referred to as 'outercourse'.
There are many who insist that oral sex, where the penis enters another person's mouth, can be classed as 'penetrative sex' while others, differ.
In some slang cultures, the term refers to the gathering of police or law enforcement offices.
It should be noted that sexual unions today, are based on pleasure, and even in the animal world, there are species that do not engage in sex only when the female is at a heighten state of fertility.
This includes chimps, dolphins.
Copulation is also believed to improve social bonding among those involved. Though in humans it can be more for simple sexual gratification, than bonding.
Without a sexual connotation, copulation can refer to the joining or linking of ideas, or thoughts.
It isn't often used in that context, however in some circles it is, in which it refers to the joining of two ideas or thoughts, to form one single theory or concept.
These instances, refer to the act of union of a concept or thought or is referring to how they are related.