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In autocatalysis, a chemical species accelerates its own production. This is a chemical reaction mechanism, not merely any process with positive feedback. An autocatalytic pathway can also be masked by competing reactions. ^[ref]

A simple idealized model using the law of mass action iswhere $a$ and $x$ are concentrations and $k>0$ is a rate constant. If $a$ is maintained constant, $x$ grows exponentially. In a closed constant-volume system with no other reactions, $a+x=c$ is conserved, soa logistic equation. The initial increase slows as the feedstock is exhausted. Exactly $x(0)=0$ remains zero in this ideal model; a separate uncatalyzed pathway changes that prediction. Thus an accelerating or sigmoidal trace alone does not identify a unique microscopic mechanism. ^[ref]

Raphaël Plasson analyzed autocatalysis with collaborators, distinguishing mechanisms that produce superficially similar self-accelerating behaviour. Their study compared chemical mechanisms, kinetic equations and dynamical patterns rather than defining every increasing reaction rate as autocatalytic.^[ref]

For the idealized reaction $A+B\to 2B$, law of mass action gives $\dot{b}=kab$; with conserved $a+b=c$, this becomes $\dot{b}=kb(c-b)$. The product promotes its own formation, but substrate depletion limits indefinite exponential growth. The kinetic assumptions and uncatalyzed background pathway matter when identifying an experimental autocatalytic effect.