1. 1. Codebase and Platform: One of the key differences between Cocoa (OS X) and UIKit is the codebase and platform they are developed for. Cocoa is primarily targeted for developing applications for macOS, which means it is designed to work on desktop or laptop computers running Mac operating system. On the other hand, UIKit is specifically developed for iOS platform, focusing on the development of applications for iPhone, iPad, and iPod touch devices. This fundamental difference in the target platforms leads to variations in available functionalities and design considerations.

2. 2. Interface Elements: Another significant difference lies in the interface elements provided by Cocoa and UIKit. Cocoa primarily uses AppKit framework to provide interface elements for OS X applications. This includes elements such as windows, buttons, menus, and other controls that are optimized for usage on desktop interfaces. On the other hand, UIKit utilizes its framework to offer interface elements optimized for touch-based interactions on iOS devices. This includes elements like navigation bars, tab bars, table views, and other touch-specific controls.

3. 3. App Development Approach: Cocoa and UIKit also differ in their app development approach. Cocoa's development approach focuses on the traditional desktop application development paradigm, where windows and multitasking are central to the user experience. It provides extensive support for working with multiple windows, managing document-based interfaces, and handling complex data models. UIKit, on the other hand, follows a more mobile-centric development approach that revolves around single-screen applications and touch-based interactions. It provides intuitive gesture recognition, navigation patterns, and view controllers for building iOS applications.

4. 4. Design Patterns and Guidelines: Design patterns and guidelines for user interfaces also differ between Cocoa and UIKit. Cocoa follows macOS Human Interface Guidelines, which emphasize consistency, simplicity, and discoverability on the Mac platform. It encourages the usage of standard interface elements and behaviors familiar to Mac users. UIKit adheres to iOS Human Interface Guidelines, which focus on clarity, deference, and depth in mobile interfaces. It promotes touch-driven interactions, large, legible text, and minimalist design principles to enhance usability on iOS devices.

5. 5. Support for Specific Features: Cocoa and UIKit support specific features that are tailored to their respective platforms. Cocoa provides functionalities such as access to Mac-specific frameworks, advanced graphics, support for user defaults and preferences, and integration with system services like Spotlight and Siri. UIKit offers features like integration with iOS-specific frameworks, support for push notifications, Core Location services, camera and photo library access, and deep integration with other iOS apps through app extensions.

6. 6. Development Tools and Environment: The development tools and environment for Cocoa and UIKit also differ. Cocoa primarily uses Xcode, Apple's integrated development environment (IDE), for coding, debugging, and building macOS applications. It includes tools like Interface Builder for designing user interfaces, Interface Inspector for inspecting UI elements, and asset catalogs for managing image assets. UIKit relies on Xcode as well but for developing iOS applications. It includes tools like Storyboard for visually designing app flows, Auto Layout for building adaptive layouts, and asset catalogs for managing app icons and images specific to iOS devices.

In summary, Cocoa and UIKit differ in terms of their targeted platforms, interface elements, app development approach, design patterns, support for platform-specific features, and development tools. These differences arise due to the diverse nature of macOS and iOS platforms, their respective user interfaces, and the distinct user experiences they aim to provide.