There are always feminine and masculine forms for nouns that describe living beings, professions, ethnical groups and substantivated adjectives, and there are always feminine and masculine forms of adjectives. Both follow the same logic. Things that are not living have only one gender, even though there is no logic how to know which one it is.
In English there are some similar examples for feminine and masculine forms, even though it is not as widely used as in French or even German. It makes one wonder how come in times of political correctness and emancipation. However, this a language course not a socio-cultural discussions club, therefore we will not follow this line of thought.
widow <=> widower
The pattern, according to which the differentiation between masculine and feminine is made is not a simple one. There are different suffixes (morphemes) to indicate a feminine form.
Ends the masculine form on s, n, t, d, an e is added and the end-consonant is voiced