Human bonding in the context of "Homophily"

Sexual intercourse (also coitus or copulation) is a sexual activity typically involving the insertion of the erect male penis inside the female vagina and followed by thrusting motions for sexual pleasure, reproduction, or both. This is also known as vaginal intercourse or vaginal sex. Sexual penetration is an instinctive form of sexual behaviour and psychology among humans. Other forms of penetrative sexual intercourse include anal sex (penetration of the anus by the penis), oral sex (penetration of the mouth by the penis or oral penetration of the female genitalia), fingering (sexual penetration by the fingers) and penetration by use of a dildo (especially a strap-on dildo), and vibrators. These activities involve physical intimacy between two or more people and are usually used among humans solely for physical or emotional pleasure. They can contribute to human bonding.

There are different views on what constitutes sexual intercourse or other sexual activity, which can impact views of sexual health. Although sexual intercourse, particularly the term coitus, generally denotes penile–vaginal penetration and the possibility of creating offspring, it also commonly denotes penetrative oral sex and penile–anal sex, especially the latter. It usually encompasses sexual penetration, while non-penetrative sex has been labeled outercourse, but non-penetrative sex may also be considered sexual intercourse. Sex, often a shorthand for sexual intercourse, can mean any form of sexual activity. Because people can be at risk of contracting sexually transmitted infections during these activities, safer sex practices are recommended by health professionals to reduce transmission risk.

A sibling is a relative that shares at least one parent with the other person. A male sibling is a brother, and a female sibling is a sister. A person with no siblings is an only child.

While some circumstances can cause siblings to be raised separately (such as foster care or adoption), most societies have siblings grow up together. This causes the development of strong emotional bonds, with siblinghood considered a unique type of relationship. The emotional bond between siblings is often complicated and is influenced by factors such as parental treatment, birth order, personality, and personal experiences outside the family.

Human sexual activity, human sexual practice or human sexual behaviour is the manner in which humans experience and express their sexuality. People engage in a variety of sexual acts, ranging from activities done alone (e.g., masturbation) to acts with another person (e.g., sexual intercourse, non-penetrative sex, oral sex, etc.) or persons (e.g., orgy) in varying patterns of frequency, for a wide variety of reasons. Sexual activity usually results in sexual arousal and physiological changes in the aroused person, some of which are pronounced while others are more subtle. Sexual activity may also include conduct and activities which are intended to arouse the sexual interest of another or enhance the sex life of another, such as strategies to find or attract partners (courtship and display behaviour), or personal interactions between individuals (for instance, foreplay or BDSM). Sexual activity may follow sexual arousal.

Human sexual activity has sociological, cognitive, emotional, behavioural and biological aspects. It involves personal bonding, sharing emotions, the physiology of the reproductive system, sex drive, sexual intercourse, and sexual behaviour in all its forms.

Grief is the response to the loss of something deemed important, in particular the death of a person or animal to which a bond or affection was formed. Although conventionally focused on the emotional response to loss, grief also has physical, cognitive, behavioral, social, cultural, spiritual, political and philosophical dimensions. While the terms are often used interchangeably, bereavement refers to the state of loss, while grief is the reaction to that loss.

The grief associated with death is familiar to most people, but individuals grieve in connection with a variety of losses throughout their lives, such as unemployment, ill health or the end of a relationship. Loss can be categorized as either physical or abstract; physical loss is related to something that the individual can touch or measure, such as losing a spouse through death, while other types of loss are more abstract, possibly relating to aspects of a person's social interactions.