<s>
In	O
systems	O
analysis	O
,	O
a	O
one-to-one	B-Application
relationship	O
is	O
a	O
type	O
of	O
cardinality	B-Application
that	O
refers	O
to	O
the	O
relationship	O
between	O
two	O
entities	O
(	O
see	O
also	O
entity	B-Architecture
–	I-Architecture
relationship	I-Architecture
model	I-Architecture
)	O
A	O
and	O
B	O
in	O
which	O
one	O
element	O
of	O
A	O
may	O
only	O
be	O
linked	O
to	O
one	O
element	O
of	O
B	O
,	O
and	O
vice	O
versa	O
.	O
</s>
<s>
In	O
mathematical	O
terms	O
,	O
there	O
exists	O
a	O
bijective	B-Algorithm
function	I-Algorithm
from	O
A	O
to	O
B	O
.	O
</s>
<s>
In	O
a	O
relational	B-Application
database	I-Application
,	O
a	O
one-to-one	B-Application
relationship	O
exists	O
when	O
one	O
row	O
in	O
a	O
table	O
may	O
be	O
linked	O
with	O
only	O
one	O
row	O
in	O
another	O
table	O
and	O
vice	O
versa	O
.	O
</s>
<s>
It	O
is	O
important	O
to	O
note	O
that	O
a	O
one-to-one	B-Application
relationship	O
is	O
not	O
a	O
property	O
of	O
the	O
data	O
,	O
but	O
rather	O
of	O
the	O
relationship	O
itself	O
.	O
</s>
<s>
A	O
list	O
of	O
mothers	O
and	O
their	O
children	O
may	O
happen	O
to	O
describe	O
mothers	O
with	O
only	O
one	O
child	O
,	O
in	O
which	O
case	O
one	O
row	O
of	O
the	O
mothers	O
table	O
will	O
refer	O
to	O
only	O
one	O
row	O
of	O
the	O
children	O
table	O
and	O
vice	O
versa	O
,	O
but	O
the	O
relationship	O
itself	O
is	O
not	O
one-to-one	B-Application
,	O
because	O
mothers	O
may	O
have	O
more	O
than	O
one	O
child	O
,	O
thus	O
forming	O
a	O
one-to-many	B-Application
relationship	O
.	O
</s>
