Yanking and deleting text will save the text to the same unnamed register. Every time you delete a word, your yanked word will be overwritten. This caused me endless amounts of frustration when I accidentally deleted a word and had to remember what I yanked earlier.

I learned that you can specify a register to save your yanked word to by prepending your yank command with "a. Where a is a register. There are a number of different registers which do different things. If you want to learn more read VIM’s register documentation.

An example usage is:

"ayw

This will save the yanked word to the register a. After deleting various things in your file you can always paste your yanked word by:

"ap

You can view the contents of all registers via the :registers command.

Even after deleting various words in your file, your yanked word will always be in register a. The VIM wiki has more details on Replacing a word with yanked text.