#Callback Code that's passed as an argument to other code and expected to call back, or execute at some time. In JavaScript, callbacks are often in the form of functions, and they're often asynchronous.
#Asynchronous Used to describe actions that do not occur at regular intervals. In the context of JavaScript, an asynchronous function or asynchronous block refers to code executing at a different time from everything else.
#Synchronous Used to describe actions that occur at regular intervals. In the context of JavaScript and Ruby, synchronous code runs and finishes before moving on to the next task.
#TDD See Test-driven development
#Test-driven development A development workflow that involves creating tests for a feature that initially fail, then writing code to make the tests pass.
#Namespace A container used to organize various objects.
#Closure An inner function that has access to the outer (enclosing) function's variables. In JavaScript, closures allow the ability to control access to data.
#Singleton A design pattern where there's only one instance of a class/pattern.