Mass numberThe mass number (symbol A, from the German word: Atomgewicht, "atomic weight"), also called atomic mass number or nucleon number, is the total number of protons and neutrons (together known as nucleons) in an atomic nucleus. It is approximately equal to the atomic (also known as isotopic) mass of the atom expressed in atomic mass units. Since protons and neutrons are both baryons, the mass number A is identical with the baryon number B of the nucleus (and also of the whole atom or ion).
Slavery in AfricaSlavery has historically been widespread in Africa. Systems of servitude and slavery were common in parts of Africa in ancient times, as they were in much of the rest of the ancient world. When the trans-Saharan slave trade, Indian Ocean slave trade and Atlantic slave trade (which started in the 16th century) began, many of the pre-existing local African slave systems began supplying captives for slave markets outside Africa. Slavery in contemporary Africa is still practiced despite it being illegal.
Baryon numberIn particle physics, the baryon number is a strictly conserved additive quantum number of a system. It is defined as where n_{\rm q} is the number of quarks, and n_{\rm \overline q} is the number of antiquarks. Baryons (three quarks) have a baryon number of +1, mesons (one quark, one antiquark) have a baryon number of 0, and antibaryons (three antiquarks) have a baryon number of −1. Exotic hadrons like pentaquarks (four quarks, one antiquark) and tetraquarks (two quarks, two antiquarks) are also classified as baryons and mesons depending on their baryon number.
Sub-Saharan AfricaSub-Saharan Africa, Subsahara, or Non-Mediterranean Africa, is the area and regions of the continent of Africa that lie south of the Sahara. These include Central Africa, East Africa, Southern Africa, and West Africa. Geopolitically, in addition to the African countries and territories that are situated fully in that specified region, the term may also include polities that only have part of their territory located in that region, per the definition of the United Nations (UN).
Lepton numberIn particle physics, lepton number (historically also called lepton charge) is a conserved quantum number representing the difference between the number of leptons and the number of antileptons in an elementary particle reaction. Lepton number is an additive quantum number, so its sum is preserved in interactions (as opposed to multiplicative quantum numbers such as parity, where the product is preserved instead). The lepton number is defined by where is the number of leptons and is the number of antileptons.
Atomic numberThe atomic number or nuclear charge number (symbol Z) of a chemical element is the charge number of an atomic nucleus. For ordinary nuclei composed of protons and neutrons, this is equal to the proton number (np) or the number of protons found in the nucleus of every atom of that element. The atomic number can be used to uniquely identify ordinary chemical elements. In an ordinary uncharged atom, the atomic number is also equal to the number of electrons.
AsiaAsia (ˈeɪʒə, UKalsoˈeɪʃə) is the largest continent in the world by both land area and population. It covers an area of more than 44 million square kilometers, about 30% of Earth's total land area and 8% of Earth's total surface area. The continent, which has long been home to the majority of the human population, was the site of many of the first civilizations. Its 4.7 billion people constitute roughly 60% of the world's population, having more people than all other continents combined.
DefinitionA definition is a statement of the meaning of a term (a word, phrase, or other set of symbols). Definitions can be classified into two large categories: intensional definitions (which try to give the sense of a term), and extensional definitions (which try to list the objects that a term describes). Another important category of definitions is the class of ostensive definitions, which convey the meaning of a term by pointing out examples. A term may have many different senses and multiple meanings, and thus require multiple definitions.
African empiresAfrican empires is an umbrella term used in African studies to refer to a number of pre-colonial African kingdoms in Africa with multinational structures incorporating various populations and polities into a single entity, usually through conquest. Listed below are known African empires and their respective capital cities. The Wabongo kingdom, with its capital in Bokanga, in the Lobaye region (South West Central African Republic) Sahelian kingdoms The Sahelian kingdoms were a series of medieval empires centred on the Sahel, the area of grasslands south of the Sahara.
Lexical definitionThe lexical definition of a term, also known as the dictionary definition, is the definition closely matching the meaning of the term in common usage. As its other name implies, this is the sort of definition one is likely to find in the dictionary. A lexical definition is usually the type expected from a request for definition, and it is generally expected that such a definition will be stated as simply as possible in order to convey information to the widest audience.
South AsiaSouth Asia is the southern subregion of Asia, which is defined in both geographical and ethnic-cultural terms. As commonly conceptualised, South Asia consists of the countries predominantly Afghanistan Bangladesh, Bhutan, India, Maldives, Nepal, Pakistan, and Sri Lanka, Topographically, it is dominated by the Indian subcontinent and defined largely by the Indian Ocean in the south, and the Himalayas, Karakoram, and Pamir mountains in the north. The Amu Darya, which rises north of the Hindu Kush, forms a part of the northwestern border.
History of AfricaThe history of Africa begins with the emergence of hominids, archaic humans and — around 300,000–250,000 years ago — anatomically modern humans (Homo sapiens), in East Africa, and continues unbroken into the present as a patchwork of diverse and politically developing nation states. The earliest known recorded history arose in Ancient Egypt, and later in Nubia, the Sahel, the Maghreb, and the Horn of Africa.
