As Google celebrates its 15th birthday, the company has announced a major change to its search algorithm called Hummingbird. Instead of matching keywords in queries, its new strategy is to manage more complex queries by attempting to understand the meanings and relationships of words and concepts.

Google makes subtle tweaks to its algorithm all the time, on the order of hundreds of time a year, but the announcement of Hummingbird is a much bigger architectural change. In a blog post, Amit Singhal, senior vice president of Google Search, explained how comparison and filter tools built into Google's "Knowledge Graph" will let users ask questions that don't necessarily have simple answers in a way that feels less like a search and more like a conversation.

"You can pull up your phone and say to Google: 'Tell me about Impressionist artists,'" Singhal explains. "You'll see who the artists are, and you can dive in to learn more about each of them and explore their most famous works. If you want to switch to Abstract artists, you can do that really easily with our new filter tool."

With the comparison tool, a simple query like "butter vs. olive oil" brings up a side-by-side comparison that shows total fat, cholesterol and calories. Google is now able to compare dog breeds, planets and so much more in ways that weren't possible before.

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The Hummingbird update also gives Google the ability to answer follow-up questions. If you search for "pictures of Great Danes" for instance, and then "common health problems," Google says it will understand that you're looking for common health problems associated with Great Danes.

Additionally, Singhal says a new Google Search app for iOS will become available in the following weeks that syncs updates across all devices. It's another step toward predictive search. If you verbally ask Google to remind you to pick up kale on your iPad the next time you're at Whole Foods for example, Google will remind you when you take your iPhone into the store.

"Ideally, you wouldn't need to pull out your phone or tap buttons to use Google, Singhal says. "We're not quite there yet, but you can already do a lot with just your voice."

Google's new changes also come with a visual update that places information on cards that Google says is optimized for touch devices.

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