Dream

Dreams are successions of images, ideas, emotions, and sensations that occur usually involuntarily in the mind during certain stages of sleep. The content and purpose of dreams are not definitively understood, though they have been a topic of scientific speculation, as well as a subject of philosophical and religious interest, throughout recorded history. The scientific study of dreams is called oneirology.

Dreams mainly occur in the rapid-eye movement (REM) stage of sleep—when brain activity is high and resembles that of being awake. REM sleep is revealed by continuous movements of the eyes during sleep. At times, dreams may occur during other stages of sleep. However, these dreams tend to be much less vivid or memorable.

The length of a dream can vary; they may last for a few seconds, or approximately 20–30 minutes. People are more likely to remember the dream if they are awakened during the REM phase. The average person has three to five dreams per night, and some may have up to seven; however, most dreams are immediately or quickly forgotten. Dreams tend to last longer as the night progresses. During a full eight-hour night sleep, most dreams occur in the typical two hours of REM.

Din

DIN or Din or din can have several meanings:

Blue

Blue is the colour between violet and green on the optical spectrum of visible light. Human eyes perceive blue when observing light with a wavelength between 450 and 495 nanometres. Blues with a higher frequency and thus a shorter wavelength gradually look more violet, while those with a lower frequency and a longer wavelength gradually appear more green. Pure blue, in the middle, has a wavelength of 470 nanometres. In painting and traditional colour theory, blue is one of the three primary colours of pigments, along with red and yellow, which can be mixed to form a wide gamut of colours. Red and blue mixed together form violet, blue and yellow together form green. Blue is also a primary colour in the RGB colour model, used to create all the colours on the screen of a television or computer monitor.

The modern English word blue comes from Middle English bleu or blewe, from the Old French bleu, a word of Germanic origin, related to the Old High German word blao. The clear sky and the deep sea appear blue because of an optical effect known as Rayleigh scattering. When sunlight passes through the atmosphere, the blue wavelengths are scattered more widely by the oxygen and nitrogen molecules, and more blue comes to our eyes. Rayleigh scattering also explains blue eyes; there is no blue pigment in blue eyes. Distant objects appear more blue because of another optical effect called atmospheric perspective.

Green

Green is the color between blue and yellow on the spectrum of visible light. It is evoked by light with a predominant wavelength of roughly 495–570 nm. In the subtractive color system, used in painting and color printing, it is created by a combination of yellow and blue, or yellow and cyan; in the RGB color model, used on television and computer screens, it is one of the additive primary colors, along with red and blue, which are mixed in different combinations to create all other colors.

The modern English word green comes from the Middle English and Anglo-Saxon word grene, from the same Germanic root as the words "grass" and "grow". It is the color of living grass and leaves and as a result is the color most associated with springtime, growth and nature. By far the largest contributor to green in nature is chlorophyll, the chemical by which plants photosynthesize and convert sunlight into chemical energy. Many creatures have adapted to their green environments by taking on a green hue themselves as camouflage. Several minerals have a green color, including the emerald, which is colored green by its chromium content.