  In this paper, we generalize the Weinberg's procedure to determine the
comoving curvature perturbation $\cal R$ to non-attractor inflationary regimes.
We show that both modes of $\cal R$ are related to a symmetry of the
perturbative equations in the Newtonian gauge. As a byproduct, we clarify that
adiabaticity does not generally imply constancy of $\cal R$, not even in the
$k\rightarrow 0$ limit. We then show that there exist non-equivalent
definitions of $\delta N$ that would reproduce $\mathcal{R}$ or the uniform
density curvature perturbation $\zeta$ at linear order. We have then shown that
the perturbative $\delta N$ definition in terms of difference between the
number of e-foldings of different gauges, can be extended non-perturbatively at
leading order in gradient expansion. Nevertheless, the computer friendly
definition in terms of the difference of e-foldings obtained from the evolution
of a local FRW Universe, respectively with perturbed and un-perturbed initial
conditions, might only give information about the linear order curvature
perturbations, contrary to what stated in the literature.
