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Two

Two is the natural number following one and preceding three; as an ordinal, it is the second. In numerals it is written as 2, in Roman numerals as II, and in words as “two.” The word derives from Old English twa, related to Proto-Germanic twa- and ultimately from the Proto-Indo-European root *duo- meaning “two.”

In mathematics, two is the smallest and the only even prime number, making it fundamental to the

In science, diatomic molecules, such as O2 and N2, consist of two atoms. In logic and computer

In language and culture, the notion of two as a pair appears across traditions, often associated with

structure
of
the
integers.
All
even
numbers
are
multiples
of
two.
The
number
two
is
the
base
of
the
binary
numeral
system,
in
which
data
are
represented
with
two
symbols:
0
and
1.
It
also
indexes
dimensions,
notably
two-dimensional
space,
and
frequently
conveys
duality,
pairing,
or
a
couple,
as
in
two
items.
The
factorial
of
two
is
two
(2!),
and
basic
identities
such
as
2
×
2
=
4
and
1
+
1
=
2
reflect
its
role
in
arithmetic.
science,
truth
values
are
often
represented
as
two
states:
true
and
false
(binary
logic).
balance,
polarity,
and
complementarity.
The
prefixes
duo-
and
dy-
derive
from
the
same
Indo-European
root
and
appear
in
numerous
terms,
reflecting
the
enduring
association
of
two
with
pairing
and
cooperation.