zero in

The phrase possibly comes from adjusting a sighting mechanism of a firearm to minimise the discrepancy between where the sight points and where a bullet lands on a target.

Another possible source is the Cartesian coordinate system in mathematics. In the coordinate system, points are defined relative to an origin (point of reference) labeled O, which has an (x,y) coordinate pair of (0,0).

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zero in (third-person singular simple present zeroes in or zeros in, present participle zeroing in, simple past and past participle zeroed in)

1. To focus one's aim; to zoom in and center (on something).

   The pilot zeroed in on the bunker and launched a guided missile.

   Zero in and find a watermark in the image.

   • 1981 September 15, day@RAND-UNIX, “C debugging”, in fa.unix-wizards‎ (Usenet):

     When you invoke the VAX C compiler with -p for profiling it generates an assembly-language call to a profiling subroutine for which I substituted my own heap-checker, and that enabled me to zero in on a heap-violation which was caused by an array-out-of-bounds condition.

   • 2021 December 6, Andrew E. Kramer, “Companies Linked to Russian Ransomware Hide in Plain Sight”, in The New York Times‎, →ISSN:

     The Biden administration has also zeroed in on the building, Federation Tower East, the tallest skyscraper in the Russian capital.

2. To successfully narrow down a search (for).

   We have zeroed in on the source of the problem.

   See if you can zero in on the caller.

3. To concentrate or focus one's attention (on a task).

   Coordinate term: tune in

   One member of the check fraud team will zero in on the fingerprints.

   • 2010, Elizabeth A. Armstrong, Laura Hamilton, Paula England, “Is Hooking Up Bad for Young Women? Compared to What?”, in Contexts‎, volume 9, number 3, →DOI, page 23b:

     Scholarship suggests that pop culture feminists have correctly zeroed in on sexual double standards as a key source of gender inequality in sexuality.

4. (idiomatic) To converge (on).

   At the spring sale, everyone zeroed in on the bargain clothes.

   • 2019 May 8, Barney Ronay, The Guardian‎:

     With 79 minutes gone, the most celebrated team of the modern age had been reduced to bunch of mooching, stumbling yellow-shirted spectators. A Champions League season that had seemed to be zeroing in on another coronation for Lionel Messi had been wrenched, gleefully, the other way.

Often, though not exclusively, in the combination "zero in on (something)".

• zeorin