= Chain-growth termination
<Chain-growth termination> removes the ability of a reactive chain carrier to continue the succession of growth steps.<IUPAC Compendium of Chemical Terminology, fifth edition (Gold Book) by International Union of Pure and Applied Chemistry>[termination, T06274, definition; source recommendation p. 1173]{ref} Two illustrative outcomes have different molecule counts:
$$
\begin{aligned}
P_j^*+P_k^*&\longrightarrow P_{j+k}, &&\Delta(C,A,S)=(-1,-2,0),\\
P_j^*+P_k^*&\longrightarrow P_j+P_k, &&\Delta(C,A,S)=(0,-2,0).
\end{aligned}
$$
The first joins the two chains into one inactive <polymer> <molecule>. The second leaves two inactive <polymer> <molecules>, as can occur when one chain end transfers <hydrogen> to the other instead of their ends joining. End-group chemistry is suppressed in these unit-count symbols; they are not complete <molecular formulas>. Losing two <polymerization-active sites> does not mean losing two chains or any incorporated <monomeric units>. A temporarily inactive, reactivatable site must not be counted as irreversible <chain-growth termination>.
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