leap second
LowTechnical, Scientific, Formal
Definition
Meaning
A one-second adjustment applied to Coordinated Universal Time (UTC) to keep it in sync with astronomical time, which is based on the Earth's rotation.
A unit of timekeeping, added occasionally to UTC, to account for the slight slowing of the Earth's rotation and maintain alignment between atomic clocks and solar time.
Linguistics
Semantic Notes
This is a compound noun referring to a specific, discrete, and internationally coordinated technical adjustment. It is a countable noun (e.g., 'a leap second,' 'the leap second,' 'two leap seconds').
Dialectal Variation
British vs American Usage
Differences
No difference in meaning. Usage is identical. The phrase originates from international timekeeping standards.
Connotations
Purely technical in both varieties.
Frequency
Equally rare in both dialects, confined to timekeeping, astronomy, computing, and related technical contexts.
Vocabulary
Collocations
Grammar
Valency Patterns
A leap second was added [to UTC] in June.The [positive/negative] leap second corrected the discrepancy.They had to account for the leap second in the software.Vocabulary
Synonyms
Neutral
Weak
Vocabulary
Antonyms
Usage
Context Usage
Business
Rare. Might be mentioned in tech company announcements about system updates for time-sensitive transactions. 'The financial trading platform will be paused for the insertion of the leap second.'
Academic
Used in physics, astronomy, geophysics, and computer science. 'The paper analyzes the long-term need for leap seconds in civil timekeeping.'
Everyday
Extremely rare. Might appear in a news article about time. 'Did you know they added an extra second to the clock last night?'
Technical
Core usage. Discussed in timekeeping standards, network protocols (e.g., NTP), and software engineering. 'The NTP server must be configured to handle the leap second flag correctly.'
Examples
By Part of Speech
verb
British English
- The timekeeping authorities will leap-second the atomic timescale.
American English
- The system is designed to leap-second the server clock.
adjective
British English
- The leap-second adjustment caused a minor glitch.
American English
- We need a leap-second patch for the software.
Examples
By CEFR Level
- Scientists sometimes add a leap second to the clock.
- A leap second makes the last minute of the day longer.
- The International Earth Rotation Service decides when to introduce a leap second.
- Because the Earth's rotation is slowing, leap seconds are occasionally necessary to keep our clocks accurate.
- The debate over abolishing the leap second centres on the technical complications it introduces for global navigation systems.
- Software engineers must account for the potential of a 61-second minute when a positive leap second is applied.
Learning
Memory Aids
Mnemonic
Think of the Earth 'leaping' very slowly, like a tired runner, so our clocks have to 'leap' a second to catch up.
Conceptual Metaphor
TIME IS A MEASURABLE ENTITY / TIMEKEEPING IS SYNCHRONIZATION.
Watch out
Common Pitfalls
Translation Traps (for Russian speakers)
- Avoid a direct word-for-word translation like 'прыжковая секунда'. The correct term is 'високосная секунда' or more technically 'секунда координации'.
Common Mistakes
- Using it as a verb (e.g., 'The clock will leap second').
- Confusing it with 'leap year'.
- Omitting the article (e.g., 'They added leap second'). It is countable.
Practice
Quiz
What is the primary purpose of a leap second?
FAQ
Frequently Asked Questions
Not on a regular schedule. They are announced by the IERS (International Earth Rotation and Reference Systems Service) typically six months in advance, whenever the difference between UTC and astronomical time (UT1) approaches 0.9 seconds.
A leap year adds a full day (February 29) to correct for the fact that a solar year is about 365.25 days. A leap second adds one second to correct for tiny, irregular changes in the Earth's rotational speed.
In theory, yes. If the Earth's rotation were to speed up significantly, a negative leap second could be declared, making a minute only 59 seconds long. However, as the Earth's rotation is generally slowing, only positive leap seconds have been added so far.
It can cause problems for precise computer systems, financial networks, and satellite navigation, which rely on continuous, unbroken time signals. Some organisations propose letting atomic and solar time drift apart very slowly instead.