<s>
In	O
object	B-Language
oriented	I-Language
programming	I-Language
,	O
viscosity	B-Application
refers	O
to	O
the	O
ease	O
at	O
which	O
a	O
developer	O
can	O
add	O
design-preserving	O
code	O
to	O
a	O
system	O
.	O
</s>
<s>
If	O
it	O
is	O
easier	O
to	O
add	O
a	O
hack	O
than	O
it	O
is	O
to	O
add	O
code	O
that	O
fits	O
into	O
the	O
program	O
's	O
design	O
,	O
then	O
the	O
system	O
has	O
high	O
viscosity	B-Application
.	O
</s>
<s>
If	O
it	O
is	O
easy	O
to	O
add	O
new	O
code	O
to	O
the	O
program	O
while	O
maintaining	O
the	O
design	O
,	O
then	O
the	O
program	O
has	O
low	O
viscosity	B-Application
.	O
</s>
<s>
The	O
name	O
is	O
a	O
metaphor	O
for	O
viscosity	B-Application
in	O
liquids	O
.	O
</s>
