The female heir is called the heiress.
The feminine version of heir is heiress.
The noun for a male is an heir; the noun for a female is an heiress.
Heir is the male version of the word.
The female version would be an heiress.
Do you mean testator? If an heir receives a bequest, the testator is the person that gives the bequest to him/her.
Heir is the masculine of heiress.
alkalies are the opposite of acids and ha have heir pH higher than seven in the pH scale.