Which language can be used to define Spark job definitions?

PySpark is a powerful tool that enables the use of Python to define Spark job definitions. As part of Apache Spark, PySpark provides an interface for programming with Spark in the Python programming language. This allows data engineers and developers to leverage the full capabilities of Spark's distributed computing framework while using the syntax and features of Python.

Using PySpark, users can perform data manipulation, analysis, and machine learning tasks, making it an integral part of working with Spark jobs. It includes functionalities for data processing with DataFrames, RDDs, and other Spark features specifically designed for handling large datasets in a distributed environment.

The other options, while useful in their respective contexts, do not provide the necessary capabilities or syntax to define Spark jobs. Transact-SQL is primarily for managing and querying relational databases, PowerShell is a task automation and configuration management framework primarily for Windows, and JavaScript is mainly used for web development rather than data processing with Spark.