Here's how to determine the oxidation number of H in NaH:

* Na (Sodium) is an alkali metal, and alkali metals always have an oxidation number of +1 in their compounds.

* The overall charge of the compound (NaH) is zero.

To balance the charge, the hydrogen atom must have an oxidation number of -1.

Therefore, the oxidation number of H in NaH is -1.