If you have an iPad, iPhone, or iPod touch, you’ve likely already heard about and upgraded to iOS 5. The latest version of Apple’s mobile OS is packed with new features and functions — including some that aren’t obvious. Want to take advantage of the hidden features in iOS 5? Here’s a quick breakdown of some of most impressive hidden features available now for your iPhone, iPad, or iPod touch.

Built in Dictionary
If you often receive emails or text with words that you’ve never heard of before, you could always use Safari to search for the definition (or even reach for the nearest real dictionary in your office or classroom). With iOS 5, users can now instantly find the definition of any word they read or type on their phone. Just highlight the word and tap it, and then choose the new option to define the word. It’s a useful feature even when you’re not sure if you’re typing the right word, or right variation of a word, preventing embarrassment when sending a quick email to a colleague or other important person.

Usage
Android users have lauded the ability to see which apps are taking up the most space on their phone. Now, the same function is baked into iOS 5 for iPad, iPhone, and iPod touch users. To see a list of all apps running and those taking up the most data, choose Usage under General in the Settings option of your iOS device. You’ll then see a list, sorted by size, of apps that are taking up the most space you on your device. You can even delete a data-greedy app right from the list.

Accessibility Options
Apple has always included Accessibility options for iOS to help make reading and using the phone easier for those with impaired vision or hearing. Some of the new options for accessibility with iOS 5 could now help make the phone easier to use for everyone. Along with previous accessibility options, such as an option for white on black text or large text, you can now set custom vibrations for each contact in your phone, so that you know who is calling without needing ringtones, and without even needing to look at your phone. A new LED flash is also an option for alerts, which originates from your camera’s flash. Be warned, though: this is a very bright flash and nothing like notification lights on the Android or even a BlackBerry. Other options include the ability to turn on triple click home as well as assisted touch, which uses gestures to allow you to control what is on your iPhone (as opposed to tapping or clicking buttons).

Emoji
Emoji has recently emerged as a popular way to add emotion and personality to text-based conversation, with mobile devices like Android supporting the characters via plugins and Mac OS X supporting Emoji, too. Now, iOS 5 features a hidden keyboard of just Emoji characters, accessible in the General section of Settings by tapping Keyboard, and then selecting International Keyboards. From there, choose Emoji (among other languages). You will then be able to swap between your normal keyboard and Emoji when composing a message using iOS 5. You can also find an option to create shortcuts in the Keyboard settings, which essentially create macros to help you compose messages using iOS 5 faster.

We have heard about a few other hidden features of iOS 5 — including the ability to now access your camera from the lock screen and take a picture the “up” volume button. We want to know, though, what hidden iOS 5 features have you discovered? Let us know in the comments.