How can I include the words molecule and mole in an equation without looking like this molecule and mole ?

Hi! Whenever I write molecule and mole in an equation (for proper labeling of units) it starts to look like this $m o \le c \underline{e}$ and $m o \le$ . How can I avoid this without compromising the units? Thank you! :)

le looks like $\le$ without quotation marks and like $\text{le}$ with.
ul looks like ul without quotation marks and like $\text{ul}$ with.
Similarly, if you try to write dtheta, it would look like $\mathrm{dt} h \eta$, but you'd probably want $d \theta$, which can be written using d theta. :)