There are many kinds of relationship that occur in everyday life. Some of these describe how the members of a family are related to each other: parent, child, brother, sister, sibling. We could also have a relation called is in for cities and countries: for example, London is in Great Britain, and Paris is in France. Or we could have a relation that describes which make of car is produced by which manufacturer. Relations are used in mathematics to describe how two numbers are related to each other; for example expressions like x < y and p ≥ q use the relations < and ≥.
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