scan

SKAN/skæn/

Noun pluralscans

14 meanings of scan

1
verbtransitive
To look over a place or group quickly while searching for someone or something.
He scanned the horizon for any sign of the missing boat.
Drivers scan the road ahead for hazards.
Similarsurvey, search, sweep, scour, watch
2
verbtransitive
To produce an image of something by means of a scanner.
The technician scanned the patient's chest to check for fractures.
We scan old film negatives to preserve them digitally.
Similarimage, digitize
Note
The office and the hospital share this use: a photograph goes through a scanner, and internal organs are imaged by computed tomography. The verb can also take the scanned thing as its subject, describing how well it takes the process: pencil drawings don't scan very well. The image that comes out is itself called a scan.
3
verbtransitive
To inspect, analyze, or go over something, often to find something in particular.
Security software scans every file for known threats.
Inspectors scan the bridge for cracks after each winter.
Similarcheck, search, inspect, examine, screen
Note
Computing turns the close look into a search with a target, and the target is introduced by for: a program scans a hard drive for errors, or a file for threats. Without for, the object is simply the ground being covered. The construction is the useful part, because scan X for Y says both where the search happens and what it hopes to find.
4
verbtransitive
To read something using an electronic device.
Shoppers scan the QR code to view the menu.
The reader scanned her badge and unlocked the door.
Similarread, swipe
Note
Here nothing is pictured. The device reads a pattern, such as a barcode, a QR code or a ticket, and the point is the data rather than an image of it. That is what separates this use from scanning to make an image. Codes, tickets and badges are the typical objects, while documents and photographs belong to the imaging sense.
5
nouncountable
The image or output produced by a scanner.
The scan revealed a hairline fracture in the wrist.
Radiologists compared the new scan with last year's images.
Similarimage, picture
6
nouncountable
A single occasion on which something is examined or imaged in one pass.
The patient underwent a full-body scan before surgery.
The technician ran a second scan to confirm the first.
Similarexamination, screening, test, check
Note
The noun names the event, not its product. Operators leave the room during the scan, and in Philip Haigh's 2024 report on a ticketing dispute a rail company pays conductors "two pence per scan." The noun is countable and easily counted, one pass of the machine at a time. What the doctors study afterward is the scan as output.
7
verbtransitive
To examine something carefully, critically, or step by step; to scrutinize.
She scanned the contract line by line before signing.
Experts scan each painting closely to detect forgeries.
Similarscrutinize, examine, study, inspect, peruse
Oppositeskim
Note
Here the looking is slow and deliberate, taken part by part. In Dune (1965) a man scans the horizon "slowly," listening and watching for the signs he has been taught. The quick-glance meaning uses the same verb for the opposite pace. When the difference matters, let an adverb settle it: scan carefully, scan closely, scan line by line.
8
nouncountable
A careful, thorough reading of something.
A thorough scan of the report revealed several errors.
He gave the contract a careful scan before signing it.
Similarperusal
Oppositeskim, glance
Note
The noun keeps the verb's double pace. A scan of a report can be thorough or hurried, and the same synonym, perusal, covers both this careful reading and the quick skim. The word alone will not tell the reader which you mean, so an adjective usually does the work: a careful or close scan, against a quick or brief one.
9
nouncountable
A quick, cursory reading; a skim.
A quick scan of the headlines told him the gist.
She gave the email a brief scan and moved on.
Similarskim, glance, look, once-over, browse
Oppositescrutiny, study
10
verbtransitive
To read or mark a line of verse so as to show its specific meter.
She scanned the sonnet to reveal its iambic pattern.
Pupils scan each line to mark the stressed and unstressed syllables.
Note
The English word began here: Middle English scanne meant marking off verse to show its metrical structure, from a Late Latin use of the verb for climbing. Francis Barton Gummere's A Handbook of Poetics (1886) holds that anyone with a good ear will scan verse correctly without instruction. In this use a reader does the work. When the line itself is the subject, it is verse that scans.

11
verbintransitive
Of a line of verse, to conform to a metrical structure.
The couplet scans perfectly in iambic pentameter.
Several lines fail to scan because of an extra syllable.
Note
A line of verse gets its own verb here: it scans, or it fails to. The verb is at home in verdicts such as scans well, scans perfectly and doesn't scan. In Milton Acorn and Cedric Smith's play The Road to Charlottetown (1998), a speaker defends a line that "doesn't scan very well in the English" by insisting that in the Gaelic it is sheer poetry.
12
verbtransitive
To perform lexical analysis on text; to break it into tokens.
The lexer scans the source file and emits a stream of tokens.
First the tools scan the input, then they parse it.
Similartokenize, lex
Note
Compiler writers use the word for the first pass over source text, in which a stream of characters is cut into tokens. In this use scan and tokenize are interchangeable, and the object is the input itself: a file, a string, a line of code. It is easily confused with the searching sense, but nothing is being hunted for here. Every character is consumed and classified.
13
nouncountable
A higher-order function that applies a binary operation across a sequence, starting from an initial accumulator, and returns the sequence of intermediate results.
A scan over the list produces every partial sum along the way.
Unlike a fold, a scan returns all the intermediate results.
Note
Functional programmers set it beside the fold. Both thread an accumulator through a sequence, but the fold reports only where it ends, while the scan reports every stop along the way. With addition, a scan turns a list of numbers into running totals, also called prefix sums. Watch the length of the result: some implementations include the starting accumulator, making the output one element longer than the input.
14
verbobsoletetransitive
To climb by steps; to go through something step by step.
Note
The meaning sits closest to the Latin scandō, "I climb," which comes from a root for jumping and climbing. Byron could still write in 1816 of "matchless heights I dare to scan," where climbing and surveying blur together. The use is obsolete now, and a modern reader will hear only looking. Use scan for climbing only as a deliberate archaism.

Practice

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Origin

This comes from late Middle English scanne, "to mark off verse to show metrical structure," from Late Latin scandere ("to scan verse"). That in turn came from Classical Latin scandō ("I climb, rise, mount"), from the Proto-Indo-European root *skend- ("to jump, dart, climb, scan").