Leif Johnson, Macworld:

Many past iOS releases let you look up definitions with a built-in dictionary with “Look Up,” but with iOS 12, we get access to a built-in thesaurus as well. As a writer, I find this a godsend. My beloved Oxford American Writer’s Thesaurus was one of the casualties of iOS’s transition to 64-bit apps, but now it’s part of the operating system itself.

Even better, the feature works with most iOS word processing apps. The only catch is that you’ll have to turn it on. Here’s how to do it.

Not sure why, but my Thesaurus was enabled already. It might be something I did long ago to add the Thesaurus to my list of iOS dictionaries.

No matter, Leif does a nice walkthrough and if you write on a regular basis, a Thesaurus is a handy thing to have.