In Egyptian mythology, the god of night, the
desert, and of all evils. He was the murderer
of Osiris, and is portrayed as a grotesque
animal.

2.
In mathematics, any collection of defined
things (elements), provided the elements are
distinct and that there is a rule to decide
whether an element is a member of a set. It
is usually denoted by a capital letter and
indicated by curly brackets . For example,
let L represent the set that consists of all
the letters of the alphabet. The symbol `E'
stands for `is a member of'; thus p `E' L
means that p belongs to the set consisting of
all letters, and 4 `~E' L means that 4 does
not belong to the set consisting of all
letters. There are various types of sets. A
finite set has a limited number of members,
such asletters of the alphabet; an infinite
set has an unlimited number of members, such
asall whole numbers; an empty or null set has
no members, such as the number of people who
have swum across the Atlantic Ocean, written
as or `empty set'; a single-element set has
only one member, such as days of the week
beginning with M, written asMonday. Equal
sets have the same members; for example, if W
=days of the week and S =Sunday, Monday,
Tuesday, Wednesday, Thursday, Friday,
Saturday, it can be said that W = S. Sets
with the same number of members are
equivalent sets. Sets with some members in
common are intersecting sets; for example, if
R =red playing cards and F =face cards, then
R and F share the members that are red face
cards. Sets with no members in common are
disjoint sets, such asminerals andvegetables.
Sets contained within others are subsets; for
example,vowels is a subset ofletters of the
alphabet. Sets and their in errelationships
are often illustrated by a Venn diagram.