When you put something into a place or into an object, you "fill" it.

simplepastpast participle
  • The server filled my glass with water.
  • You should fill your gas tank soon. It’s almost empty.
  • Fill it up? (This question is often used at gas stations when the attendant asks you if you want to a full tank of gas.)
  • I filled my bowl with cereal.
  • His pockets are filled with change.
  • The auditorium is filled with people.

When the word "fill" is used with the preposition "in" or "out," it describes the action of writing something on a form or on empty lines:

  • You have to fill out this form with personal information. (You need to provide your name, address, phone number, etc.)
  • John filled out an application.
  • Sarah filled out an entry form for a contest.
  • Make sure you fill in all the blanks on the test. (You have to provide answers on blank lines.)
  • I forgot to fill in a few blanks on an online form, so it was rejected.

"Fill in" is an idiom that means to provide information:

  • What’s the problem? Can you fill me in?
  • Please fill him in on how to operate this machine.
  • Our supervisor filled us in on the new health care program at work.

Click here to go to the Word of the Day page.

First published on March 3, 2012.