Sexual tension
Sexual tension is a social phenomenon that occurs when two individuals interact and one or both feel sexual desire, but the consummation is postponed or never happens. A common scenario is where the two individuals function in close proximity, such as co-workers or in a group of friends, but do not have sex to avoid awkwardness. Another common scenario is when two people's attraction is limited to physical, with there being no emotional attraction.
Sexual tension can also occur when two individuals have previously had sexual relations and still feel an attraction towards each other, but do not wish to have sex again for fear of its effect on their current social situation (such as maintaining a relationship with a different partner). It can also be felt in situations when two individuals have a relation devoid of physical contact, as in a long-distance relationship.
Sexual tension often occurs between friends when the relationship is close and often flirtatious, yet the two people involved adamantly deny their feelings for each other to themselves, and to others. Meanwhile, it can be extremely obvious to other friends/co-workers that such tension is present between the two individuals. It can be said that, often when people give in to sexual tension, the relationship can become complicated and awkward if no new relationship level is established, as the relationship that existed before the sex is, in a way, no longer valid.
It is a common feature of plot and characterization in works of fiction. This longing is often suggested by incidents of intimacy; for instance, when two people or characters are alone and in close proximity (or actually touching), yet desire is never explicitly expressed. Another common theme is for characters to develop an interest in one another over the course of the plot, and if this is expertly done, the audience can become aware of the growing attraction.