What is the process called that reduces the size of a file?

The process that reduces the size of a file is known as compression. Compression involves encoding information using fewer bits than the original representation, which helps to decrease the amount of disk space that a file occupies. There are various algorithms employed for this process, such as ZIP or JPEG, which can minimize file sizes significantly without necessarily losing crucial information. This is particularly beneficial for storage and quicker transmission over networks, where smaller files can be sent more efficiently.

By contrast, decompression refers to expanding a file back to its original size after it has been compressed. Compilation refers to the process of converting source code written in a programming language into machine code that a computer's processor can execute, and concatenation is the process of linking together two or more files into a single file. None of these processes relates to reducing the file size.