I'm having a hard time figuring out the difference between underlying and underneath...

For instance, The Free Dictionary definition for both wasn't helpful:

Lying under or beneath something


In or to a place beneath; below

Also, I couldn't find any particular difference Google searching for "it uses * underlying" and "it uses * underneath".

  • Have you tried looking them up in a dictionary?
    – DJMcMayhem
    Commented Apr 2, 2015 at 17:35
  • @DJMcMayhem The Free Dictionary gives "Lying under or beneath something" for one and "In or to a place beneath; below" for the other. Not much of a difference for me.
    – talles
    Commented Apr 2, 2015 at 17:40
  • I have never heard "underlying" defined that way. I usually hear it used as "to be the foundation, cause, or basis of". merriam-webster.com/dictionary/underlie
    – DJMcMayhem
    Commented Apr 2, 2015 at 17:43
  • What is more confusing is the difference between underlying and underpinning, in my humble opinion. Commented May 6, 2017 at 4:07

1 Answer 1


Semantically they're very similar, but syntactically, the difference is that underlying is an adjective, whereas underneath is either a preposition or an adverb.

The syntactic difference means that, like most adjectives, underlying usually occurs before the noun it modifies...

This sentence illustrates my underlying point.

...but note that we can also use it as a "continuous verb form", with "point" as the subject...

The point underlying that sentence is made again here.

Apart from that syntactic difference, note that the relatively less common underlying usually refers to something fundamental, that underpins something else, whereas underneath (and plain under) merely implies something being (physical or figuratively) below something else.

  • Great answer. In my Google search example, "it uses something underneath" would be the correct way to phrase it?
    – talles
    Commented Apr 2, 2015 at 18:23
  • 1
    @talles: I don't know what you're trying to say there. You'd need to explain the exact context in which you might be uncertain about which word to use. In most cases if you give a full sentence, only one would be valid, or the meaning would change according to which word you used. Commented Apr 2, 2015 at 18:28
  • @FumbleFigers In my case something is a software (a library to be more specific).
    – talles
    Commented Apr 2, 2015 at 19:37
  • @talles - It's a thorny question question when applied to software, for a couple reasons. (1) Software isn't physical, so the sense of "under" doesn't apply (not in the sense of one is on top, the other is under). (2) Software is relatively new (software libraries even more so), so there isn't as much precedent for how words like beneath would apply.
    – J.R.
    Commented Apr 2, 2015 at 21:04
  • In any case, this is why we implore people to include Details in their questions. By itself, "What is the difference between underlying and underneath?" can go a few different ways (the first of which is, "What does the dictionary say?"). Of the many ways to answer that question, most of them won't help you determine whether a software library is running underneath a system, or if we should say something about the underlying code in a library. (It's best not to ask about "somethings" when you have something more specific in mind.)
    – J.R.
    Commented Apr 2, 2015 at 21:08

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