intervene

verb

1. (intransitive)To become involved in a situation, so as to alter or prevent an action.

   “The police had to be called to intervene in the fight.”

   “Nature film-makers are discouraged from intervening in the events they are attempting to capture on film.”

2. (intransitive)To occur, fall, or come between, points of time, or events.

   “An instant intervened between the flash and the report.”

   “I hadn't seen him since we were in school, and the intervening years had not been kind to him.”

   “[…] it is plain, that shaking off a Power, which Force, and not Right, hath set over any one, though it hath the Name of Rebellion; yet is no Offence before God, but that which he allows and countenances, though even Promises and Covenants, when obtain’d by force, have intervened.”

   “Even sad vicissitude amus’d his soul; And if a sigh would sometimes intervene, And down his cheek a tear of pity roll, A sigh, a tear, so sweet, he wish’d not to controul.”

   “She counted the days that must intervene before their invitation could be sent; hopeless of seeing him before.”

3. (intransitive)To occur or act as an obstacle or delay.

   “Nothing intervened to prevent the undertaking.”

   “For while so near each other thus all day Our task we choose, what wonder if so near Looks intervene and smiles, or object new Casual discourse draw on, which intermits Our dayes work brought to little,”

   “I reproach’d my self with my Easiness, that would not sow any more Corn one Year than would just serve me till the next Season, as if no Accident could intervene to prevent my enjoying the Crop that was upon the Ground;”

   “[…] a numbness, an occasional stupor, fell upon my mind even in the midst of my terrors, until sleep at last intervened, and in my sea-tossed coracle I lay and dreamed of home […]”

   “He kept the fire brightly blazing, for he knew that it alone intervened between the flesh of his body and their hungry fangs.”

4. (ambitransitive)To say (something) in the middle of a conversation or discussion between other people, or to respond to a situation involving other people.

   “Young Scarfe stared, astounded. “You haven’t met before,” Mrs. Gould intervened. “Mr. Decoud—Mr. Scarfe.””

   ““That sounds suspiciously like bigotry to me,” intervened Maitland, sweetening his impertinence with a dimpled smile.”

   “They all talked nonstop. That is, if you didn’t intervene. They were accustomed to being interrupted.”

5. (ambitransitive)To come between, or to be between, persons or things.

   “The Mediterranean intervenes between Europe and Africa.”

   “1668, Joseph Glanvill, Plus Ultra, or, The Progress and Advancement of Knowledge since the Days of Aristotle, London: James Collins, Chapter 11, p. 79, How defective the Art of Navigation was in elder Times, when they Sailed by the observation of the Stars, is easie to be imagin’d: For in dark weather, when their Pleiades, Helice, and Cynosura were hidden from them by the intervening Clouds, the Mariner was at a loss for his Guide, and exposed to the casual conduct of the Winds and Tides.”

   “If the profits of the merchant importer or merchant manufacturer were taxed, equality seemed to require that those of all the middle buyers, who intervened between either of them and the consumer, should likewise be taxed.”

   “[…] small fields and miniature meadows, separated […] by wild self-sown woodlands of birch, alder, holly, mountain ash, and hazel, that meander through the valley, intervening the different estates with natural sylvan marches […]”

   “Venters calculated that a mile or more still intervened between them and the riders.”

6. In a suit to which one has not been made a party, to put forward a defense of one's interest in the subject matter.

   “an application for leave (i.e. permission) to intervene”