Keeping Google's phone offerings straight can be a chore.
There's Motorola, the company it bought a couple years back. Then there are the various "Google Play Editions" of popular smartphones from other manufacturers, with the makers' proprietary software stripped out.
Finally, there are the Nexus phones, flagship devices made to Google's specifications and designed to introduce new versions of the company's Android operating system.
I've been using the latest of these, the Nexus 5. It's the first device to run Android 4.4, dubbed "KitKat" in the company's sweet-treat naming system, and the two make for a pleasant if not dazzling combination.
As with last year's Nexus 4, Google has turned to LG Electronics to manufacture the phone, which is handsome in a generic sort of way.
The corners are rounded and the soft-grip back is ever so slightly bowed; the five-inch display is surrounded by extremely thin side bezels, keeping the dimensions manageable even one- handed. At about a third of an inch thick, it slides comfortably into pocket or purse.
The 445-pixels-per-inch display exceeds both Apple's iPhone 5s and Samsung's Galaxy S4 -- though your eye can't detect any difference -- and it weighs 4.59 ounces, which is less than the Nexus 4.
The most important change from its predecessor, though, is the inclusion of support for LTE, the fastest so-called 4G networks.
Both Sprint and T-Mobile, the two U.S. carriers selling the Nexus 5 directly, are still fairly early in their LTE deployment. But it will also run over AT&T's much larger LTE network.
The nicest thing is you get to choose: Google is selling the phone, unlocked, at the bargain price of $349 with 16 gigabytes of storage, or $399 with 32 GB. (Unfortunately, Google says the phone won't work on Verizon, the carrier with the largest LTE footprint.)
The Nexus 5 bears more than a passing similarity to LG's considerably more expensive G2, sharing similar displays and a potent Qualcomm Snapdragon processor. But its battery is less powerful, and the front and rear cameras aren't as good.
While I could get through a day of light-to-moderate use on the Nexus 5, streaming a two-and-a-half hour movie left a fully charged battery at 2 percent. And the eight-megapixel camera, while adequate for most purposes, was sometimes slow to focus, with colors seeming washed out in less-than-perfect lighting conditions. You can do much better.
Still, the Nexus 5 is a lot of phone for the money, as long as you don't ask too much of it. As for KitKat, the new version of Android, it's a step backward -- and I mean that in a good way.
As a general rule, new operating systems are designed to run best on the latest and greatest hardware. But that can pose problems for people with older devices, as some users of Apple's iOS 7 have discovered.
The Android situation is even worse: Newer versions of the software don't run on many older or less powerful devices, leaving users and developers adrift in a sea of incompatibility.
With KitKat, Google has re-engineered Android to allow it to run on lower-end devices, in the hope that more existing phones will be able to update to it and new, less-expensive devices, many of them being sold in emerging markets, will run it out of the box.
Of course, it runs just fine on higher-end devices like the Nexus 5, where it can do some new tricks.
One is support for a listening mode: Saying "OK, Google" from the home screen allows you to immediately dictate a search query or issue a command such as "Open the Netflix app." It's similar to, though not as powerful as, a feature introduced earlier this year in Motorola's Moto X phone that works even when the screen is dark.
Meanwhile, Google Now, the personal assistant, resides a fingerswipe to the right from the home screen, and Google has made some of the privacy settings more accessible -- like the one that tells it not to scan all your Gmail attachments looking for packages to track, a feature I always find particularly creepy.
There are other new features as well, including built-in support for step-counting and other fitness-related apps and the ability to search for nearby businesses from within the phone dialer screen.
I'm less enamored of the consolidation of all texts, video calls and Google chat messages into a single hub called Hangouts, which feels more like an effort to promote the Google+ social network than something that really serves users.
KitKat is a modest step forward for Android -- but it may be more important to Google than to the people who use it.