  We introduce a truncated $M$-fractional derivative type for
$\alpha$-differentiable functions that generalizes four other fractional
derivatives types recently introduced by Khalil et al., Katugampola and Sousa
et al., the so-called conformable fractional derivative, alternative fractional
derivative, generalized alternative fractional derivative and $M$-fractional
derivative, respectively. We denote this new differential operator by
$_{i}\mathscr{D}_{M}^{\alpha,\beta }$, where the parameter $\alpha$, associated
with the order of the derivative is such that $ 0 <\alpha<1 $, $\beta>0$ and $
M $ is the notation to designate that the function to be derived involves the
truncated Mittag-Leffler function with one parameter.
  The definition of this truncated $M$-fractional derivative type satisfies the
properties of the integer-order calculus. We also present, the respective
fractional integral from which emerges, as a natural consequence, the result,
which can be interpreted as an inverse property. Finally, we obtain the
analytical solution of the $M$-fractional heat equation and present a graphical
analysis.
