crack(noun) and halfway(adjective or adverb) are different in terms of part of speech. Then why are they in a parallel structure?

Consider the story of two men quarreling in a library. One wants the window open and the other wants it closed. They bicker back and forth about how much to leave it open: a crack, halfway, or three‑quarters of the way. No solution satisfies them both. Enter the librarian. She asks one why he wants the window open: “To get some fresh air.” She asks the other why he wants it closed: “To avoid a draft.” After thinking a minute, she opens wide a window in the next room, bringing in fresh air without a draft. This story is typical of many negotiations. Since the parties’ problem appears to be a conflict of positions, they naturally tend to talk about positions — and often reach an impasse. The librarian could not have invented the solution she did if she had focused only on the two men’s stated positions of wanting the window open or closed. Instead, she looked to their underlying interests of fresh air and no draft.

Negotiation: Theory and Strategy

2 Answers 2


In this context, "a crack" is a noun acting as an adverb.

Take the simplified version of two of these sentences:

Leave the window open halfway.
Leave the window open a crack.

With both sentences, we can replace the part in bold with the same expression:

Leave the window open this much.

If we make it a question, we can see it's an adverb:

Q: How open is the window?
It's open halfway.
It's open a crack.

If "a crack" were a noun acting as a noun here, the expression that replaced it would be a pronoun, like "that" or "it", and the question would be "What is the window open", which is bad grammar.

  • 1
    I love your answer! Grammar books tend to talk about parts of speech only as they would be listed in a dictionary, when you must also often consider what function they perform in a given sentence, which is a different level of analysis and often important. For example, the question "How are you?" seems to call for a response with an adverb, but it can be answered with any of "I am well," "I'm good," or "I'm feeling tired," depending on what meaning you want to convey. Feb 22, 2022 at 15:40

If something is open "a crack", it is open slightly. "A crack", "halfway", and "three-quarters of the way" are all adverbial phrases in this context.

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