Ido, unlike Esperanto, does not assume the male sex by default. For example, Ido does not derive the word for “waitress” by adding a feminine suffix to “waiter”, as Esperanto does. Instead, Ido words are defined as sex-neutral, and two different suffixes derive masculine and feminine words from the root: ' for a waiter of either sex, ' for a male waiter, and ' for a waitress. There are only two exceptions to this rule: First, ' for “father”, ' for “mother”, and ' for “parent”, and second, ' for “man”, ' for “woman”, and "" for “adult”.