= Left Grassmann derivative
{title2=$\partial_\theta^L$}
Left differentiation with respect to an odd <Grassmann variable> is the odd linear operation $\partial_\theta^L\theta=1$, with zero derivative on every other generator. For a homogeneous element $a$ of parity $|a|$, it obeys the graded product rule
$$
\partial_\theta^L(ab)=(\partial_\theta^La)b+(-1)^{|a|}a(\partial_\theta^Lb).
$$
For independent odd generators, $\partial_{\bar\theta}^L(\theta\bar\theta)=-\theta$. This sign comes from moving the derivative through the first odd factor in the <Grassmann algebra>. It fixes chirality in the <chiral-superfield component expansion>; an ordinary commuting-variable product rule would give the wrong sign.
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