Hello, dear student!
There is a wonderful category of nouns in the Russian language, which are related to common gender. What does it mean? It means, there are the nouns that can belong to masculine gender as well as to feminine one. Usually we fasten nicknames, name people or refer them to a definite class. It is necessary to look closer at these words in order to address such complex issue:
"Сирота" (orphan) – we can't say for sure to what gender belongs this word, an orphan can be as a boy as a girl. You need to look at a context and define by implication to what gender belongs this word. You can also look at other parts of speech which surely will give you a clue.
Usually nouns of common gender are used by Russian-speaking people in informal speech, but you can also see them in different texts. Such words impart emotional coloring to text – as positive as negative one:
"Плакса" – usually we call like this a person who always cries (weeps).
"Ябеда" – a person who always complains to somebody.
"Неряха" – a person who doesn't stick to the order, he/she is careless and inaccurate.
"Калека" – a person who doesn't have any body part, but in most cases we name people who are unpleasant and ugly in our opinion this way.
"Сладкоежка" – a person who likes sweets very much and eats them in large quantities.
"Коллега" – a person who works with someone in a business environment, department or on a project.