I am confused by fill and fill in. I checked online, and both forms are used in

  • fill a hole

  • fill in a hole

So I am wondering is there any difference in meaning between them? If not, what's the meaning of in? What is the function of in "fill in"?

8 Answers 8


There are some differences in wider usage. 'Fill' can be something that is designed as a container as well as a hole, whereas 'fill in' implies that it will be filled once and then left that way. 'Fill in' can also be used to mean to inform or to complete.

edit: and in fact it is this meaning of completion that is reflected in only being filled once.


I fill my cup.

Makes sense, whereas

I fill in my cup.

doesn't make sense.

Other uses of 'fill in'

I filled in the rest of the detail on the canvas.

I'll fill you in later.


In this context, to me, fill in suggests that the hole is removed, i.e. filled with the substance of its surroundings. Fill could mean this too, but is a little less particular. Other than that they seem about the same.

For example, "The man was so big that he completely filled the hole" expresses that the hole was occupied by a large man. But you wouldn't say the man "filled in" the hole.


I would use fill to describe something that is repeatedly made full and then depleted, such as the water bottle, or your belly. Fill up would further describe that it was filled to capacity, you would say you filled up the bottle or you only filled it halfway. Fill in would describe a hole in the ground that is filled to capacity with native material, thereby ceasing to be a hole. In the same sense you would say I filled in the crack with caulk, thereby eliminating the crack. I believe fill in and fill out can be used interchangeably in regards to a form or document, most likely regional preferences.


At least in this case, they can be used interchangeably with no difference in meaning. Both mean "to put a substance into a hole or crack to make a surface level". Hope it helps.


Fill In is a phrasal verb of Fill.

Fill a hole.

Fill in a hole.

There is no such wondering thing.


Confusion about "to fill a hole" and "to fill in a hole"

Sometimes you can use the simple verb and a compound verb as well and there is actually no great difference. When you use the compound particle "in" the underlying idea is you fill in material to make the hole vanish.


I'd reckon fill in will seldom appear in the sense of filling, apart from filling in a form (some information)

In my experience, fill in is most commonly used in the sense of "substitute" .

Here is the Wordnet overview of fill in

  1. fill in — (supply with information on a specific topic; "He filled me in on the latest developments")
  2. shade, fill in — (represent the effect of shade or shadow on)
  3. substitute, sub, stand in, fill in — (be a substitute; "The young teacher had to substitute for the sick colleague"; "The skim milk substitutes for cream —we are on a strict diet")
  4. complete, fill out, fill in, make out — (write all the required information onto a form; "fill out this questionnaire, please!"; "make out a form")

Both of them can be used without almost no difference in meaning, but that is a matter of context they are being used in. For example:

She filled her bottle with water.= makes sense She filled in her bottle with water.= doesn't really sound right. Besides these there is also fill out which I think means to make something fuller.

EXAMPLE: To fill out this dress.= you need to eat more. To fill out a form= means to make it fuller because it starts out plain and empty, but then becomes filled out(fuller) as it gains more contents.

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