需

1. Necessity and Requirement: That which is indispensable; an objective or situational necessity.

2. Waiting and Expectation: To pause in a poised state of readiness while awaiting the fulfillment of a prerequisite.

3. Sustenance: The act of maintaining strength or nourishment during a period of waiting (notably in the Yi Jing).

• Verb: To need; to require; to wait for.
• Noun: A necessity; a requirement; the duration of waiting.
• Modal/Adverbial: Indicating that an action is mandatory or required by circumstances ("must").

• vs. 待 (dài): While both involve waiting, dài typically emphasizes awaiting a specific person or event, whereas xū emphasizes the necessity or deficiency that makes the wait inevitable.
• vs. 要 (yào): xū tends toward external, situational, or cosmic requirements; yào more frequently denotes personal desire, immediate intent, or subjective will.

Associated with hexagram ䷄ of the Yi Jing, representing the state of sustaining oneself while danger prevents immediate advance.

The term often slides between "the void" (the lack/need) and "the interval" (the duration of the wait). In strategic or philosophical contexts, consider if the waiting is protective—a calculated delay to avoid hazard by not advancing prematurely.