Last fall, Google rolled out a word-of-the-day feature for Search. Powered by its Knowledge Graph, the feature sent you a notification every day teaching you a new word and its definition. It isn't clear how popular the feature might be, but Google has recently adjusted how it works slightly. You can now configure the word of the day to offer three different levels of difficulty: Intermediate, Advanced, and Expert.
We knew this change was coming since Google announced the feature in October, when the company explicitly said that we'd be able to choose different difficulty levels in the future. Those that already have the feature enabled should see a notification from the Google app prompting them to customize the "word level," as spotted by 9to5Google. If you don't see the notification, or you haven't enabled the feature yet, you can also configure the difficulty through the pane that appears when enabling it.
Just search for any old definition on your phone and tap the bell icon in the top right. You'll see the three options and a handful of examples for each. Pick the level you want, and you'll get daily notifications teaching you a new word at around that degree of difficulty.
Aspiring logophiles can turn the level up or down as they optate. "Advanced" seems to be the default, but you can turn that down to offer slightly simpler or more sesquipedalian words, as required.