Many nouns tell you the gender of the person or animal they are referring to, which means whether it is male or female.
We use the term masculine when we are referring to male words and feminine for female words.
Often the suffix ess is added to a masculine word to create its feminine version.
If the masculine word ends in er or or, the 'e' or 'o' is usually dropped before adding the suffix ess.
tiger + ess = tigress