EventNett keywords and categories
Each event and location can be given up to 20 keywords (often called  to help classify them into similar categories. When adding keywords to an event or location or when including them in the search panel, keywords must be separated by spaces and must not contain any non-alphanumeric characters.
One way that EventNett keywords are different from tags elsewhere is that keywords can have synonyms. When a keyword is given a synonym, searches using that synonym will return items as if the keyword were used. So, if the keyword "theater" has the synonyms "cinema" and "theatre", searches using either "cinema" and "theatre" will return events and locations that have the "theater" keyword. Synonyms can be added from the Keywords tab in the admin view. Synonyms eliminate the issue of having similar tags, but they also introduce the risk of over-generating search results. If a keyword is given too many synonyms, even very specific keyword searches may return a large number of results. Because of this, synonyms should be added carefully.
Another way the EventNett keywords differ from tags is how they are used to create categories. The categories are not a fixed list but actually the 10 most popular keywords in EventNett, so they can change over time. This method was chosen as a compromise between creating a rigid structure of classifications having keywords alone classify objects.