1. Syntax: Lua uses a simple and lightweight syntax with fewer rules compared to Objective-C, which has a strict syntax and requires adhering to certain patterns and conventions in coding.
2. Type System: Lua is dynamically typed language, while Objective-C is a statically typed language, meaning variable types are determined at runtime in Lua and at compile time in Objective-C.
3. Memory Management: Objective-C utilizes manual memory management using retain-release cycles and autorelease pools, whereas Lua has automatic memory management with garbage collection, reducing the need for explicit memory management.
4. Platform Support: Objective-C is primarily used for iOS and macOS development, whereas Lua is often used for scripting, game development, and embedded systems across different platforms such as mobile, desktop, and web.
5. Concurrency: Objective-C lacks built-in support for concurrency and threading, requiring developers to utilize tools like Grand Central Dispatch, while Lua has built-in support for coroutines and lightweight threading mechanisms for concurrency.
6. Usage: Objective-C is commonly used for developing native applications, especially on Apple platforms, while Lua is used for scripting, game development, and extending applications due to its simplicity and flexibility.

In Summary, Lua and Objective-C differ in syntax, type system, memory management, platform support, concurrency handling, and usage in software development.