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3 (three) is a number, numeral and digit. It is the natural number following 2 and preceding 4, and is the smallest odd prime number and the only prime preceding a square number. It has religious and cultural significance in many societies.

5 (five) is a number, numeral and digit. It is the natural number, and cardinal number, following 4 and preceding 6, and is a prime number.

Humans, and many other animals, have 5 digits on their limbs.

A bedroom or bedchamber is a room situated within a residential or accommodation unit characterised by its usage for sleeping. A typical western bedroom contains as bedroom furniture one or two beds, a clothes closet, and bedside table and dressing table, both of which usually contain drawers. Except in bungalows, ranch style homes, ground floor apartments, or one-storey motels, bedrooms are usually on one of the floors of a dwelling that is above ground level. Beds range from a crib for an infant; a single or twin bed for a toddler, child, teenager or single adult; to bigger sizes like a full, double, queen, king or California king). Beds and bedrooms are often devised to create barriers to insects and vermin, especially mosquitoes, and to dampen or contain light or noise to aid sleep and privacy.

CADR may refer to:

• CAR and CDR, a programming language construct used in Common Lisp or Scheme
• CADR, the name of a computing system developed at M.I.T.; see Lisp machine
• Clean Air Delivery Rate, a rating system developed for portable room air cleaners
• Continuous Adiabatic Demagnetisation Refrigeration, a multi-stage magnetic refrigeration system
• Center for Alternative Dispute Resolution, an institution that provides training and accreditation

A cleaner, cleanser, cleaner or cleaning operative is a type of industrial or domestic worker who does the cleaning. A janitor (US and Canada), also known as a custodian, porter or caretaker, is a person who cleans and might also carry out maintenance and security duties. A similar position, but usually with more managerial duties and not including cleaning, is occupied by building superintendents in the United States and Canada and by site managers in schools in the United Kingdom.

Cleaner in Cambridge English dictionary means: "a person whose job is to clean houses, offices, public places, etc.:", in Collins dictionary: "A cleaner is someone who is employed to clean the rooms and furniture inside a building.". However, a cleaner does not always have to be employed and perform work for pay, such as in the case of volunteer work or community service. "Cleaner" may also refer to cleaning agents e.g. oven cleaner, or devices used for cleaning, eg. vacuum cleaner.

Cleaning operatives may specialize in cleaning particular things or places, such as window cleaners, housekeepers, janitors, crime scene cleaners and so on. Cleaning operatives often work when the people who otherwise occupy the space are not around. They may clean offices at night or houses during the workday.

Dust is made of fine particles of solid matter. On Earth, it generally consists of particles in the atmosphere that come from various sources such as soil lifted by wind (an aeolian process), volcanic eruptions, and pollution.

Dust in homes is composed of about 20–50% dead skin cells. The rest, and in offices and other built environments, is composed of small amounts of plant pollen, human hairs, animal fur, textile fibers, paper fibers, minerals from outdoor soil, burnt meteorite particles, and many other materials which may be found in the local environment.

H, or h, is the eighth letter of the Latin alphabet, used in the modern English alphabet, including the alphabets of other western European languages and others worldwide. Its name in English is aitch (pronounced , plural aitches), or regionally haitch , plural haitches.

A home, or domicile, is a space used as a permanent or semi-permanent residence for one or more human occupants, and sometimes various companion animals. It is a fully- or semi-sheltered space and can have both interior and exterior aspects to it. Homes provide sheltered spaces, for instance rooms, where domestic activity can be performed such as sleeping, preparing food, eating and hygiene as well as providing spaces for work and leisure such as remote working, studying and playing.

Physical forms of homes can be static such as a house or an apartment, mobile such as a houseboat, trailer or yurt or digital such as virtual space. The aspect of 'home' can be considered across scales; from the micro scale showcasing the most intimate spaces of the individual dwelling and direct surrounding area to the macro scale of the geographic area such as town, village, city, country or planet.

The concept of 'home' has been researched and theorized across disciplines – topics ranging from the idea of home, the interior, the psyche, liminal space, contested space to gender and politics. The home as a concept expands beyond residence as contemporary lifestyles and technological advances redefine the way the global population lives and works. The concept and experience encompasses the likes of exile, yearning, belonging, homesickness and homelessness.

Light, visible light, or visible radiation is electromagnetic radiation that can be perceived by the human eye. Visible light spans the visible spectrum and is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 terahertz. The visible band sits adjacent to the infrared (with longer wavelengths and lower frequencies) and the ultraviolet (with shorter wavelengths and higher frequencies), called collectively optical radiation.

In physics, the term "light" may refer more broadly to electromagnetic radiation of any wavelength, whether visible or not. In this sense, gamma rays, X-rays, microwaves and radio waves are also light. The primary properties of light are intensity, propagation direction, frequency or wavelength spectrum, and polarization. Its speed in vacuum, 299792458 m/s, is one of the fundamental constants of nature. Like all types of electromagnetic radiation, visible light propagates by massless elementary particles called photons that represents the quanta of electromagnetic field, and can be analyzed as both waves and particles. The study of light, known as optics, is an important research area in modern physics.

The main source of natural light on Earth is the Sun. Historically, another important source of light for humans has been fire, from ancient campfires to modern kerosene lamps. With the development of electric lights and power systems, electric lighting has effectively replaced firelight.

Night or nighttime is the period of darkness when the Sun is below the horizon. The opposite of nighttime is daytime. Sunlight illuminates one side of the Earth, leaving the other in darkness. Earth's rotation causes the appearance of sunrise and sunset. Moonlight, airglow, starlight, and light pollution dimly illuminate night. The duration of day, night, and twilight varies depending on the time of year and the latitude. Night on other celestial bodies is affected by their rotation and orbital periods. The planets Mercury and Venus have much longer nights than Earth. On Venus, night lasts 120 Earth days. The Moon's rotation is tidally locked, rotating so that one of the sides of the moon always faces Earth. Nightfall across portions of the near side of the Moon results in lunar phases visible from Earth.

Organisms respond to the changes brought by nightfall, including darkness, increased humidity, and lower temperatures. Their responses include direct reactions and adjustments to circadian rhythms, governed by an internal biological clock. These circadian rhythms, regulated by exposure to light and darkness, affect an organism's behavior and physiology. Animals more active at night are called nocturnal and have adaptations for low light, including different forms of night vision and the heightening of other senses. Diurnal animals are active during the day and sleep at night; mammals, birds, and some others dream while asleep. Fungi respond directly to nightfall and increase their biomass. With some exceptions, fungi do not rely on a biological clock. Plants store energy produced through photosynthesis as starch granules to consume at night. Algae engage in a similar process, and cyanobacteria transition from photosynthesis to nitrogen fixation after sunset. In arid environments like deserts, plants evolved to be more active at night, with many gathering carbon dioxide overnight for daytime photosynthesis. Night-blooming cacti rely on nocturnal pollinators such as bats and moths for reproduction. Light pollution disrupts the patterns in ecosystems and is especially harmful to night-flying insects.

Historically, night has been a time of increased danger and insecurity. Many daytime social controls dissipated after sunset. Theft, fights, murders, taboo sexual activities, and accidental deaths all became more frequent due in part to reduced visibility. Cultures have personified night through deities associated with some or all of these aspects of nighttime. The folklore of many cultures contains "creatures of the night," including werewolves, witches, ghosts, and goblins, reflecting societal fears and anxieties. The introduction of artificial lighting extended daytime activities. Major European cities hung lanterns housing candles and oil lamps in the 1600s. Nineteenth-century gas and electric lights created unprecedented illumination. The range of socially acceptable leisure activities expanded, and various industries introduced a night shift. Nightlife, encompassing bars, nightclubs, and cultural venues, has become a significant part of urban culture, contributing to social and political movements.

An office is a space where the employees of an organization perform administrative work in order to support and realize the various goals of the organization. The word "office" may also denote a position within an organization with specific duties attached to it (see officer or official); the latter is an earlier usage, as "office" originally referred to the location of one's duty. In its adjective form, the term "office" may refer to business-related tasks. In law, a company or organization has offices in any place where it has an official presence, even if that presence consists of a storage silo, for example, instead of a more traditional establishment with a desk and chair. An office is also an architectural and design phenomenon, including small offices, such as a bench in the corner of a small business or a room in someone's home (see small office/home office), entire floors of buildings, and massive buildings dedicated entirely to one company. In modern terms, an office is usually the location where white-collar workers carry out their functions.

In classical antiquity, offices were often part of a palace complex or a large temple. In the High Middle Ages (1000–1300), the medieval chancery acted as a sort of office, serving as the space where records and laws were stored and copied. With the growth of large, complex organizations in the 18th century, the first purpose-built office spaces were constructed. As the Industrial Revolution intensified in the 18th and 19th centuries, the industries of banking, rail, insurance, retail, petroleum, and telegraphy grew dramatically, requiring many clerks. As a result, more office space was assigned to house their activities. The time-and-motion study, pioneered in manufacturing by F. W. Taylor (1856–1915), led to the "Modern Efficiency Desk" of 1915. Its flat top, with drawers below, was designed to allow managers an easy view of their workers. By the middle of the 20th century, it became apparent that an efficient office required additional control over privacy, and gradually the cubicle system evolved.

Pollen is a powdery substance produced by most types of flowers of seed plants for the purpose of sexual reproduction. It consists of pollen grains (highly reduced microgametophytes), which produce male gametes (sperm cells). Pollen grains have a hard coat made of sporopollenin that protects the gametophytes during the process of their movement from the stamens to the pistil of flowering plants, or from the male cone to the female cone of gymnosperms. If pollen lands on a compatible pistil or female cone, it germinates, producing a pollen tube that transfers the sperm to the ovule containing the female gametophyte. Individual pollen grains are small enough to require magnification to see detail. The study of pollen is called palynology and is highly useful in paleoecology, paleontology, archaeology, and forensics. Pollen in plants is used for transferring haploid male genetic material from the anther of a single flower to the stigma of another in cross-pollination. In a case of self-pollination, this process takes place from the anther of a flower to the stigma of the same flower.

Pollen is infrequently used as food and food supplement. Because of agricultural practices, it is often contaminated by agricultural pesticides.

Purifier(s) may refer to:

• Air purifier, a device that filters pollution out of the air
• Water purification, removing contaminants from water, sometimes using a water purifier
• The Purifiers, a 2004 action film
• Purifiers (Marvel Comics), a fictional terrorist organization

In kinematics, the speed (commonly referred to as v) of an object is the magnitude of the change of its position over time or the magnitude of the change of its position per unit of time; it is thus a non-negative scalar quantity. The average speed of an object in an interval of time is the distance travelled by the object divided by the duration of the interval; the instantaneous speed is the limit of the average speed as the duration of the time interval approaches zero. Speed is the magnitude of velocity (a vector), which indicates additionally the direction of motion.

Speed has the dimensions of distance divided by time. The SI unit of speed is the metre per second (m/s), but the most common unit of speed in everyday usage is the kilometre per hour (km/h) or, in the US and the UK, miles per hour (mph). For air and marine travel, the knot is commonly used.

The fastest possible speed at which energy or information can travel, according to special relativity, is the speed of light in vacuum c = 299792458 metres per second (approximately 1079000000 km/h or 671000000 mph). Matter cannot quite reach the speed of light, as this would require an infinite amount of energy. In relativity physics, the concept of rapidity replaces the classical idea of speed.