Most research databases allow for a symbol to be used at the end of a word to retrieve variant endings of that word. This is known as truncation. For example, in Education Abstracts, the "$" is used as a truncation symbol. By placing this at the end of a root word, such as work$, you will retrieve all words beginning with that root (work, worker, workforce, workplace, etc.).
Be careful using truncation! If you want to retrieve items about cats, don't truncate the word cat. If you do, you will also retrieve cataclysm, catacomb, catalepsy, catalog, etc., etc. It's best to use the boolean operator "or" in these instances (cat or cats). In some databases, such as Lexis-Nexis Academic, the database will automatically search for simple plurals.
Some databases allow for wild cards to be embedded within a word to replace a single character. For instance, in Education Abstracts, you can also use $ within a word to replace characters. For example, comp$tion finds composition, competition, computation, etc. You can also limit the number of characters that the wild card symbol represents. For example, theat$2 finds theater or theatre, but not theaters, theatrical, etc.. Truncation comes in handy when you want to pick up both American and English spellings. For instance, behavi$or retrieves behavior and behaviour.
The symbols used for truncation and universal characters often vary from database to database. To determine the symbols in the database you're using, check the online help screens or ask a librarian.