Right now advertising has 420 questions, and advertisement has 23 questions.
I propose we mark the latter as a synonym for the former, since afaik they mean the exact same thing.
This also has the added benefit of nobody being able to make any jokes about the number of advertising questions, because I hate fun.
According to this related Meta discussion, the ads tag was made a synonym of the advertising tag.
Though it seemed to be agreed there that ads was short for advertisement, there isn't a synonym between the two however. Ergo, it seems logical that advertisement should also become a synonym of advertising.
In regards to because I hate fun, please note that fun is strictly considered off-topic here - JK :-)
advertisementtag was merged with and made a synonym of theadvertisingtag. This should be fully visible in a day or so.