degrees of triad isotacticity, syndiotacticity, and heterotacticity

https://doi.org/10.1351/goldbook.D01573
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:
Purple Book, 1st ed., p. 45 [Terms] [Book]