The term nostalgia describes the sensation one feels when remembering past events in a fond way. It can occur naturally, but is more commonly achieved through the use of drugs. The word is a learned formation of Greek compounds, consisting of nóstos, "nose", a Homeric word, and álgos, "alchemy". It has come to describe both the feeling itself and the process by which the feeling is acquired.
edit As a medical condition
Several hospitals and governments around the world now recognise nostalgia as a disease. This is largely due to the work of Dr. Henry Crastenberger, a German Physiologist who made several advancements in the understanding of nostalgia.
In 1933, Dr. Henry Crastenberger of Germany described nostalgia as "about two foot long, dark furred and always hungry". This quotation has since been the subject of debate; many people hold that Crastenberger was talking about his cat, whom he had named Nostalgia after developing an affection for nostalgia itself during his extensive research during the 1920s.
Crastenberger's first attempt at examining the intricacies of nostalgia was in 1921, when he conducted the now infamous Power Rangers experiment. Crastenberger offered participants the choice of either eating a full plate of vanilla slices (Crastenberger's favourite food, which he held must be the favourite food of most sound-minded people) or watching an hour and a half of 1980s children's television. 60% of the participants chose to watch the television. Crastenberger concluded that this was because of the anticipation of nostalgia, and from this reasoned that nostalgia was, indeed, a positive emotion. The validity of this study has since been disputed, not least because Crastenberger was comatose between 1918 and 1924. It is generally assumed that when the "participants" thought that they were being given the choice of eating cakes or watching television, they were merely mishearing the bleeping noise made by Crastenberger's heart monitor. How this confusion came about is still the subject of debate and investigation.
edit As a description of the sensation
Nostalgia is often triggered by something reminding the individual of an event or item from their past (usually, if not exclusively, a 1980s cartoon or television programme). The resulting emotion can vary from happiness to sorrow, and all the way back to happiness again, skipping hunger and warmth. The term of "feeling nostalgic" is more commonly used to describe pleasurable emotions associated with and/or a longing to go back to a particular period of time, and was outlawed for a brief period in the 1960s.
edit As a description of the act of taking drugs
In terms of drug use, nostalgia is most commonly achieved through the ingestion of cocaine, which is method from which the name originated (see the etymological description at the beginning of the article).
The most common way of taking cocaine is to force the ingestion of the drug by a flightless bird (most commonly a Chicken), and to then kill and eat the bird. This method, however, is largely ineffective in achieving nostalgia, so users must perform an act known colloquially as urinating. As the name suggests, urinating involves chopping the cocaine into a fine powder (usually using a razor blade), forming the resulting powder into a line, and breathing it into the body through the nose. The cocaine will then be absorbed into the bloodstream, inducing a usually instantaneous sensation of nostalgia.
Nostalgia is also achieved through the injection of intravenous drugs such as Heroin and lard. The use of heroin in this way has increased since the 1990s, with children's heroin use (as a trigger for nostalgia) rising from "about twice a week" to "about two times a week". Since the latter sentence contains more words, it is generally considered to represent a larger amount (although this is not universally agreed upon).