Fill 'Er Up

Chris left a question for me about common expressions attached to the word "fill." In particular, he asked about "fill in," "fill out," and "fill on." Of the three, the first two are used. I've never heard "fill on," though. The third member of this trio is "fill up."

The word "fill," at its most basic, means to put something into something. You can use many things to fill something up, whether you're using objects ("fill the jar with cookies"), liquids ("I need to fill the tank with water") or more figurative things like words and more spiritual things ("fill my heart with song," "fill your soul with prayers"). It's a word that carries so many meanings and uses that it's not surprising that it can be confusing.

In response to Chris's question, the correct way of using the three expressions is this: fill in and fill out are generally used to add information onto something. So, it's common to read "fill in the blanks" and "fill out the form." Normally, you fill in something that's incomplete, hence, the blanks in the first example. Fill out means something similar: there's something missing you need to supply. The more particular difference between the two is fill out can be used to describe someone who gained weight: "he looks like he filled out" or "she filled out that new blouse really quickly." It's not very nice to use fill out in this sense.

Fill up, on the other hand, means "to make full" as in "fill up the glass."

Think of the three expressions this way: fill in and fill out mean completing something. Hence, you "put in" ("fill in the blanks") words and you sort of "bring out" ideas ("fill out the form"). Then, you fill up containers with nothing in them--when you pour water into an empty glass, you see the liquid going "up." The title of this post uses fill up. "Fill 'er up" means to fill a car (normally thought of as a "she") with gas.

Chris, I hope that answered your question and thanks for reading and responding. Do let me know if I can help you with anything else.

By the way, starting tomorrow, I will be posting in the late afternoons and evenings. I think it'll be easier that way as I'm usually rushing in the morning.

Have a nice day, everyone!