The fractions of
triads in a regular vinyl
polymer that are of the
mm,
rr and
mr =
rm
types, respectively. In cases where triad analysis is not attainable, the diad isotacticity and diad syndiotacticity may be defined as the fractions of
diads in a regular vinyl polymer that are of the
m and
r types, respectively. (
m =
meso;
r =
racemic).
Source: