How do I delete a word when the cursor is in the middle of the word?

What you need is the following keystrokes in normal mode (after pressing Esc):

diw (meaning: delete inner word)

-or-

daw (meaning: delete a word)

The second command also deletes all spaces after the word, or all spaces before the word if there are no spaces after the word.

For more related commands:

:help diw
:help daw