Here is the storage mathematics and how it has changed over the years. My first Mac notebook came with a 40 MB hard drive. The small amount of storage meant a constant cropping was to get enough space so that Mac OS and various applications could run.
Over the years, hard disk drives went in price while they were in storage. Over time, storage was so cheap that we didn't have to delete files at all. Spotlight can find something with a few clicks.
Then came the MacBook Air and solid state storage (SSDs). SSDs are fast but cost far more than hard disk drives for far less storage, so we're back to trim, crop, and delete files that take up too much space. If your Mac notebook goes dry on storage, there's an app that can help. It is free.
Monolingual makes storage management the old-fashioned way. It gets rid of files you don't need and every Mac running OS X has a gigantic amount of files that are rarely used. As the name suggests, monolingual deals with language files. If all you ever use is OS X in English, the echo sounder can delete the rest of the files in a few clicks.
Nor can it be much easier to use monolingual. Open the app. Select the languages you want to remove. Click the Remove button. That's it.
How much disk space is recycled? Hundreds of megabytes, depending on how many OS X languages you delete. What if you want the languages back again (for example, if you sell your Mac or give it away as a hand-down)? Just install OS X and everything goes back to normal.
The latest version of Monolingual requires OS X 10.10.x Yosemite, but versions for older Mac and OS X are available. And it's free. So think of it as a free way to recover more storage space on your Mac.