A Nachbin family on a Hausdorff completely regular space $X$ is any collection $V$ of upper semi continuous non negative functions with some additional conditions. With such a family is associated a locally convex space $CV(X)$ consisting of all continuous scalar functions $f$ suth that $fv$ is bounded on $X$, for every $v \in V$, with the topology $\tau_V$ given by the semi norms $\|fv\|_{\infty}$, $v \in V$. A weighted topology is any topology given in this way.
Now, a locally convex topology $\tau$ on some linear space $E$ is said to be strict if the strongest locally convex topology on $E$ which coincides with $\tau$ on the bounded sets of $(E, \tau)$ is $\tau$ itself.
When is a weighted topology strict ?
It is clear that if $\tau_V$ is bornological, then it is strict. Also if $\tau_V$ is the topology $\beta$ of Buck, it is strict but not bornological.