From my experience lots of non adult pages can fall prey to Google's adult definition. For example I had a page showing nothing but PSA's and I couldn't figure out what was wrong with this one page. Then it suddenly hit me - it was about Cumming, GA. I guess Google has a dirtier mind than I do. On the bright side, at least they showed PSAs and not some adult themed ads on a family site.

But what if something, for example, is not a #*$! site but mentions the word "sex"? For example, say a scientific article that says "widgets of this sex..."

I've got several pages that are specifically about sex (hanky-panky, not gender), and they do display AdSense ads. The ads aren't always perfectly matched, though: When I looked at one of the pages just a moment ago, the #1 ad pitched a Yahoo Shopping page for "girls." ("Quickly check merchant prices. 1000s of stores.") The #5 ad was for a "Sex-crimes defense lawyer." The other three ads were a better fit for the page and the site.

I had a page ranking very high for "animal sex", basically talking of animals and of different sexes. Although think of any combination of farm anmial like dogs, cows, horses,... Since my site is trusted highly, this ranking was achieved and did receive much traffic, including displaying Adsense Ads. There was no complain by google. I did remove Adsense from the page and also cloaked the word "sex" from those pages simply to avoid trouble.

On the other hand I got a shop feed to another site of mine, and some adult toys or dvds were included. Although there was nothing like explicit material displayed, google acted pretty quickly, setting a 3 day deadline in order to remove the adsense blog or the content.

So google can see the difference between adult and adult wording. But it may also happen, that adsense will display public service ads automatically on not 100% sober pages.

Agree with Rocco. I have a relationships website where I regularly discuss intimate topics insofar as couples are concerned (it is not adult, but yes it is impossible to have a dating/relationship website and pretend as if all people do is eat out in restaurants). I think the ads are awesome and never had any issued with Google; just do not overuse explicit words and stay away from words that might be commonly used for certain acts but can trigger filters. For instance, I like the word intimacy over $%&.