<s>
In	O
mathematics	O
,	O
a	O
half-exponential	B-General_Concept
function	I-General_Concept
is	O
a	O
functional	O
square	O
root	O
of	O
an	O
exponential	O
function	O
.	O
</s>
<s>
That	O
is	O
,	O
a	O
function	O
such	O
that	O
composed	B-Application
with	O
itself	O
results	O
in	O
an	O
exponential	O
function	O
:	O
</s>
<s>
Half-exponential	B-General_Concept
functions	I-General_Concept
are	O
used	O
in	O
computational	O
complexity	O
theory	O
for	O
growth	O
rates	O
"	O
intermediate	O
"	O
between	O
polynomial	O
and	O
exponential	O
.	O
</s>
