(1) I'm up for that = someone stating their own interest/availability for what "that" refers to
Bob: "Hey, wanna go get coffee?"
Zack: "Yeah man, I'm up for that."

(2) I'm up = a) a person physically stood up or, b) a person is now conscious
Bob: "Hey, wanna go get coffee?"
Zack: "Yeah man, I'm up." *atypical

Bob: "Hey, you gonna get outta bed sometime today?"
Zack: "Yeah man, I'm up, I'm up." <- typical to my dialect

Grammatically, why does adding the prepositional phrase "for that" change the semantic meaning between (1) and (2)? Is the change because of the words "for" and "that" and their denotations? Or is it because adding a prepositional phrase ("for that" in this case) to the phrasal verb ("to be up") is triggering the semantic shift?

As a point of contrast, the meaning does not significantly change between:

(3) I'm down for that = someone stating their own interest/availability (ie for the "that")
Bob: "Hey, wanna go get coffee?"
Zack: "Yeah man, I'm down for that."

(4) I'm down = someone stating their own interest/availability
Bob: "Hey, wanna go get coffee?"
Zack: "Yeah man, I'm down."

Some additional background info, from another question I asked, in the comments, @WS2 added a valuable distinction:

@wanderling To me I'm down for that = My name is on a list/it has all been arranged that I am coming. However, I'm up for that = I am keen to be involved. Where do I sign?

And there is a question on the etymology for "I'm down for that" here at What's the origin of “I'm down with it”?, which could be similar enough to "I'm up for that" to explain its etymology as well.

  • up and down are adverbs in the usual sensevhere, no prepositions, so the tagging is wrong.
    – vectory
    Commented Mar 15, 2020 at 0:17
  • @vectory I tagged "prepositions" because of the prepositional phrase for that. And in my examples, up and down are adjectives. For example, Merriam-Webster has many definitions of down, and as an ADJ in definition 5b, it is "slang : understanding or supportive of something or someone —usually used with with". That is the context I use down here.
    – wanderling
    Commented Mar 15, 2020 at 2:57
  • 1
    “to be up for” is a phrasal verb taking an object, informally expressing a willingness to take part in an activity. “to be down for” is also a phrasal verb, with one meaning being to be on a list, as in “you can put me down for ten tickets for the charity ball.” Further research will reveal more.
    – Xanne
    Commented Mar 15, 2020 at 3:31
  • @Xanne Thanks for the comment! To paraphrase: I should consider "to be up for" in its entirety as the phrasal verb, taking the object "that"?
    – wanderling
    Commented Mar 16, 2020 at 6:11
  • @Xanne I ask for clarification, because I was considering "to be up" as the phrasal verb, to which was added the prepositional phrase "for that," where "that" was the object.
    – wanderling
    Commented Mar 16, 2020 at 6:12

2 Answers 2


The phrase "for that" does not really change the meaning, but up is just not used alone in that sense.

up is more easily understood in the denotional sense when it appears alone, because we are up most of the time. That's why down as a shortform of down for that is allowable, if I can already see that you are not physically down.

  • Please elaborate about why "for that" does not change the meaning, and where this occurs. Additionally, I do not follow the argument in the second paragraph. Are you commenting on "up" in the sense of "happy, in a good mood"? Similarly, I do not understand the connection between being physically down or "a sad mood", and being "down" for something in the slang sense of being "interested and engaged, cool." Thank you for your time.
    – wanderling
    Commented Mar 15, 2020 at 3:02
  • 1
    I could not fully answer your question, I'm sorry. Your comment is interesting, indeed I thought about "up" in the sense of "happy, in a good mood" but conciously chose not to add it, because it might be secondary to "awake" and "up for that", I expect. With physical I implied a so called "universal metaphor" in which higher equals better. In that sense, I perceive "down" as taktful humbleness instead.
    – vectory
    Commented Mar 15, 2020 at 14:42
  • Point in case, I'm down more often implies blue, disappointed, depressed.
    – vectory
    Commented Mar 15, 2020 at 14:47
  • I appreciate your answer and comments nevertheless! Discussing this has helped me understand the topic better, even if we don't achieve a clear answer. It seems then that, if i understand correctly, that in your answer considering "up" in the sense of "being awake" or "being vertical/active" is the primary way of considering "I'm up." Thus, in terms of semantics, when we say the shorthand "I'm down" and we can visually tell that the person saying "I'm down" is not actually "down," where "down" means "not up". From context we know "I'm down" then has a different semantic meaning.
    – wanderling
    Commented Mar 16, 2020 at 6:24
  • 1
    could you please add a quote for "I'm down" in the required sense to your question? I'm starting to doubt it's currency.
    – vectory
    Commented Mar 16, 2020 at 18:59


I'm up - I am awake (dressed, teeth brushed...)

I'm up for that - I like the idea of taking part in 'that'

I'm down - I am sad

I'm down for that - I have committed myself to doing 'that'

That said, both 'for that' senses can be understood without adding 'for that', context is important to be understood right.

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