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18th Century In South America
18 (eighteen) is the natural number following 17 and preceding 19. In mathematics * Eighteen is a composite number, its divisors being 1, 2, 3, 6 and 9. Three of these divisors (3, 6 and 9) add up to 18, hence 18 is a semiperfect number. Eighteen is the first inverted square-prime of the form ''p''·''q''2. * In base ten, it is a Harshad number. * It is an abundant number, as the sum of its proper divisors is greater than itself (1+2+3+6+9 = 21). It is known to be a solitary number, despite not being coprime to this sum. * It is the number of one-sided pentominoes. * It is the only number where the sum of its written digits in base 10 (1+8 = 9) is equal to half of itself (18/2 = 9). * It is a Fine number. In science Chemistry * Eighteen is the atomic number of argon. * Group 18 of the periodic table is called the noble gases. * The 18-electron rule is a rule of thumb in transition metal chemistry for characterising and predicting the stability of metal complexes. In re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Octodecimal
There are many different numeral systems, that is, writing systems for expressing numbers. By culture / time period By type of notation Numeral systems are classified here as to whether they use positional notation (also known as place-value notation), and further categorized by radix or base. Standard positional numeral systems The common names are derived Hexadecimal#Etymology, somewhat arbitrarily from a mix of Latin and Greek language, Greek, in some cases including roots from both languages within a single name. There have been some proposals for standardisation. Non-standard positional numeral systems Bijective numeration Signed-digit representation Negative bases The common names of the negative base numeral systems are formed using the prefix ''nega-'', giving names such as: Complex-base system, Complex bases Non-integer representation, Non-integer bases p-adic number, ''n''-adic number Mixed radix * Factorial number system * Even double factorial ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pentomino
Derived from the Greek word for ' 5', and "domino", a pentomino (or 5-omino) is a polyomino of order 5, that is, a polygon in the plane made of 5 equal-sized squares connected edge-to-edge. When rotations and reflections are not considered to be distinct shapes, there are 12 different ''free'' pentominoes. When reflections are considered distinct, there are 18 '' one-sided'' pentominoes. When rotations are also considered distinct, there are 63 '' fixed'' pentominoes. Pentomino tiling puzzles and games are popular in recreational mathematics. Usually, video games such as '' Tetris'' imitations and ''Rampart'' consider mirror reflections to be distinct, and thus use the full set of 18 one-sided pentominoes. Each of the twelve pentominoes satisfies the Conway criterion; hence every pentomino is capable of tiling the plane. Each chiral pentomino can tile the plane without being reflected. History The earliest puzzle containing a complete set of pentominoes appeared in H ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chai (symbol)
Chai ( he, חַי "living" ') figures prominently in modern Jewish culture; the Hebrew letters of the word are often used as a visual symbol. History According to '' The Jewish Daily Forward'', its use as an amulet originates in 18th century Eastern Europe. Chai as a symbol goes back to medieval Spain. Letters as symbols in Jewish culture go back to the earliest Jewish roots, the Talmud states that the world was created from Hebrew letters which form verses of the Torah. In medieval Kabbalah, Chai is the lowest (closest to the physical plane) emanation of God.Pelaia, Ariela.What Does the Chai Symbol Signify for Jews? ThoughtCo. (accessed March 9, 2018). According to 16th century Greek rabbi Shlomo Hacohen Soloniki, in his commentary on the Zohar, Chai as a symbol has its linkage in the Kabbalah texts to God's attribute of 'Ratzon', or motivation, will, muse. The Jewish commentaries give an especially long treatment to certain verses in the Torah with the word as their centra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hebrew Language
Hebrew (; ; ) is a Northwest Semitic language of the Afroasiatic language family. Historically, it is one of the spoken languages of the Israelites and their longest-surviving descendants, the Jews and Samaritans. It was largely preserved throughout history as the main liturgical language of Judaism (since the Second Temple period) and Samaritanism. Hebrew is the only Canaanite language still spoken today, and serves as the only truly successful example of a dead language that has been revived. It is also one of only two Northwest Semitic languages still in use, with the other being Aramaic. The earliest examples of written Paleo-Hebrew date back to the 10th century BCE. Nearly all of the Hebrew Bible is written in Biblical Hebrew, with much of its present form in the dialect that scholars believe flourished around the 6th century BCE, during the time of the Babylonian captivity. For this reason, Hebrew has been referred to by Jews as ''Lashon Hakodesh'' (, ) since a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
