The maximum end-to-end distance of a linear polymer chain. For a single-strand polymer molecule, this usually means the end-to-end distance of the chain extended to the all-trans
conformation. For chains with complex structure, only an approximate value of the contour length may be accessible. The sum of the lengths of all skeletal bonds of a single-strand polymer molecule is occasionally termed 'contour length'. This use of this term is discouraged.
Purple Book, 1st ed., p. 50 (http://old.iupac.org/publications/books/author/metanomski.html)