A mixture is not the same as a compound which is made of two or more atoms connected together. For instance, a mixture of the gases hydrogen and nitrogen contains hydrogen and nitrogen, not the compound ammonia which is made of hydrogen and nitrogen atoms.
A mixture where the different parts can be distinguished easily is called "heterogenous", one where this is not the case is called "homogeneous". A third form is called colloid.
If one substance in a mixture dissolves in the other, it is called a solution. For example, if sugar is put in water it forms a mixture, then dissolves to make a solution. If it does not dissolve, it would be called a suspension.
Solids can be mixtures also. Alloys are mixtures. Many kinds of soil and rock are mixtures of different minerals. Thus, a mixture is made of two or more elements and/or compounds which are not chemically combined.
Language family
Language families are groups of languages that are related to each other because they come from a common older language. The languages in such a family are similar in their vocabulary or structure.
For example, French and Spanish both come from Latin. Latin was spoken a long time ago, and some of the people who spoke it started to speak one way, saying, for example, for good: "bueno" while another group started saying "bon." Most words are said a little differently in Spanish and French, so the two are called different languages.
Most languages belong to a language family, but some languages do not. These languages are called Language isolates.
There also are constructed languages, like for example Esperanto. Constructed languages are made for different reasons: making a 'world language', for fun, for use in fiction, etc.
"Ethnologue" 22 (2019) lists these language families as "major". Each has at least 1% of all languages on Earth:
"Glottolog" 4.0 (2019) lists the following as the largest families, of 8494 languages:
Chess
Chess is a board game for two players. It is played in a square board, made of 64 smaller squares, with eight squares on each side. Each player starts with sixteen pieces: eight pawns, two knights, two bishops, two rooks, one queen and one king. The goal of the game is for each player to try and checkmate the king of the opponent. Checkmate is a threat ('check') to the opposing king which no move can stop. It ends the game.
During the game the two opponents take turns to move one of their pieces to a different square of the board. One player ('White') has pieces of a light color; the other player ('Black') has pieces of a dark color. There are rules about how pieces move, and about taking the opponent's pieces off the board. The player with white pieces always makes the first move. Because of this, White has a small advantage, and wins more often than Black in tournament games.
Chess is popular and is often played in competitions called chess tournaments. It is enjoyed in many countries, and is a national hobby in Russia.
Most historians agree that the game of chess was first played in northern India during the Gupta Empire in the 6th century . This early type of chess was known as "Chaturanga", a Sanskrit word for the military. The Gupta chess pieces were divided like their military into the infantry, cavalry, elephants, and chariots. In time, these pieces became the pawn, knight, bishop, and rook. The English words "chess" and "check" both come from the Persian word "shāh" meaning king.
The earliest written evidence of chess is found in three romances (epic stories) written in Sassanid Persia around 600. The game was known as "chatrang" or "shatranj". When Persia was taken over by Muslims (633–644) the game was spread to all parts of the Muslim world. Muslim traders carried the game to Russia and to Western Europe. By the year 1000 it had spread all over Europe. In the 13th century a Spanish manuscript called "Libro de los Juegos" describes the games of "shatranj" (chess), backgammon, and dice.
The game changed greatly between about 1470 to 1495. The rules of the older game were changed in the West so that some of the pieces (queen, bishop) had more scope, development of the pieces was faster, and the game more exciting. The new game formed the basis of modern international chess. Historians of chess consider this as the most important change since the game was invented.
The rules of chess are governed by the World Chess Federation, which is known by the initials FIDE, meaning "Fédération Internationale des Échecs". The rules are in the section "Laws of Chess" of the "FIDE Handbook". FIDE also give rules and guidelines for chess tournaments.
Chess is played on a square board divided into eight rows of squares called ranks and eight columns called files, with a dark square in each player's lower left corner. This is altogether 64 squares. The colors of the squares are laid out in a checker (chequer) pattern in light and dark squares. To make speaking and writing about chess easy, each square has a name. Each rank has a number from 1 to 8, and each file a letter from "a" to "h". This means that every square on the board has its own label, such as g1 or f5. The pieces are in white and black sets. The players are called White and Black, and at the start of a game each player has 16 pieces. The 16 pieces are one king, one queen, two rooks, two bishops, two knights and eight pawns.
Definitions: vertical lines are "files"; horizontal lines are "ranks"; lines at 45° are "diagonals".
Each piece has its own way of moving around the board. The "X" marks the squares where the piece can move.
Most pieces capture as they move. If a piece lands on an opponent's piece, the opposing piece is taken off the board. There are three special cases:
If a move is made which attacks the opposing king, that king is said to be 'in check'. The player whose king is checked must make a move to remove the check. The options are: moving the king, capturing the threatening piece, or moving another piece between the threatening piece and the king. If the player whose king is in danger cannot do any of these things, it is checkmate, and the player loses the game.
Once in every game, each king can make a special move, known as "castling". When the king castles, it moves two squares to the left or right. When this happens, the rook is moved to stand on the opposite side of the King. Castling is only allowed if all of these rules are kept:
"En passant" ('in passing' in French) is a special capture. It is only available when a pawn moves forward two squares past an opposing pawn on an adjacent file. The opposing pawn must be on the 5th rank from its own side. Then the opponent's pawn can capture the double-mover "as if it had only moved one square forward". This option is open on the next move only.
For example, if the black pawn has just moved up two squares from g7 to g5, then the white pawn on f5 can take it by "en passant" on g6. The "en passant" rule was developed when pawns were allowed to make their double move. The rule made it more difficult for players to avoid pawn exchanges and blockade the position. It kept the game more open.
When a pawn moves to its eighth rank, it must be changed for a piece: a queen, rook, bishop, or knight of the same color (player's choice). Normally, the pawn is "queened", but in some advantageous cases another piece is chosen, called 'under-promotion'.
Checkmates are rare in competitive chess. The most common ends are decisions made by one or both players.
The FIDE rules for competitive chess include all the above rules, plus several others.