In researching the function systems, it is too restricting to use a term like politics or political or government and then argue about which term is more appropriate. It’s far more effective to combine terms to search for a concept that is represented by a number of terms.
In other words, when searching the Google Books corpus, it makes more sense to combine search terms with the + operator. So rather than searching for government, policy, and politics separately and then worrying about which is the best term, we can combine the results to get a concept result rather than just word results. Here I have combined the terms government, policy, and political to get one result and combined economy, economic, economics to get another result so that I can compare these two function systems.
Or I can add govern and politics to the first line.
Here in an Ngram that uses the + operator for seven function systems from the year 1800-2000. It helps, for example, to combine press and media to get a more accurate result for the mass media function system. We can also combine school, education, and educate for the education function system. In German, we could use Schule and Bildung.
Below I’ve add legal+law and health+medical+medicine, and I changed the years to 1990-2000.
See this link for an explanation of the advanced search options.