degrees of cistacticity and transtacticity

https://doi.org/10.1351/goldbook.D01571
For a regular polymer containing double bonds in the main chain of the constitutional repeating units these are the fractions of such double bonds that are in the cis and trans configurations, respectively.
Source:
Purple Book, 1st ed., p. 46 (http://old.iupac.org/publications/books/author/metanomski.html)