# What Is Latency? Meaning, Examples and Latency vs Bandwidth > Latency is the delay between a request and the response, usually measured in milliseconds. - **Term:** latency - **Part of speech:** noun - **Pronunciation:** /ˈleɪtənsi/ - **English level (CEFR):** B2 - **Register:** Formal, Both - **Region:** US and UK - **Topic:** [Tech jargon](https://app.speaktechenglish.com/learn/topics/tech-jargon.md) - **Lesson:** https://app.speaktechenglish.com/learn/latency - **Last updated:** 2026-10-27 ## Meaning Latency is the delay between a request and the response, usually measured in milliseconds. Low latency means a system feels fast; high latency means users wait. Latency is the delay between a request and its response: the wait. When you click "Pay" and nothing happens for two seconds, those two seconds are latency. Engineers measure it in milliseconds (ms), and they usually talk about percentiles instead of averages. "p95 latency is 300 ms" means 95% of requests finish in 300 ms or less, and the slowest 5% take longer. At work you will hear the word in three places. In incidents: "Latency spiked right after the deploy." In design reviews: "A cache should cut read latency." In customer promises: "Our SLA guarantees p99 latency under 500 ms." Two traps for non-native speakers. First, grammar: latency is usually uncountable, so say "high latency" or "latency issues", not "a high latencies". Second, meaning: latency is not bandwidth. Latency is how long one message takes to arrive, and bandwidth is how much data can move per second. A long-distance connection can have plenty of bandwidth and still feel slow, because every round trip takes time. Say it LAY-tuhn-see, with the stress on the first syllable. Use "latency" for a measured delay, and keep "lag" for casual talk about games and video calls. ## When you hear it The database query is adding too much latency to our API response times. ## Examples - **in an incident channel:** "p95 latency on checkout jumped from 180 ms to 900 ms right after the 14:10 deploy, so I'm rolling back now." - **in a design review:** "If we put a cache in front of the user service, we should cut read latency to under 20 ms." - **in a Slack message:** "Is anyone else seeing high latency from the EU region, or is it just my connection?" - **in a customer call:** "Our SLA guarantees p99 latency under 500 milliseconds for API requests." ## What native speakers say - "We need to reduce latency across the network." - "This feature has high latency issues." - "Low latency is critical for real-time performance." ## Common mistakes - ✗ "We have a latency problem with our bandwidth." → ✓ "We have a latency problem with our response time or We have a bandwidth problem with our data throughput." (Latency and bandwidth are different concepts. Latency is delay; bandwidth is capacity.) - ✗ "The server is too latency." → ✓ "The server has high latency or The server is experiencing latency issues." (Latency is a noun, not an adjective. Use latency as a noun or use the adjective form with 'high' or 'low'.) - ✗ "We latency the system yesterday." → ✓ "We optimized latency in the system yesterday or We reduced latency yesterday." (Latency is not typically used as a verb. Use verbs like optimize, reduce, increase, or measure with latency as the object.) ## Be careful Do not confuse latency (delay in response time) with bandwidth (amount of data transferred). Latency is about speed of response, not capacity. ## Word forms | Part of speech | Word | Example | | --- | --- | --- | | noun | latency | Network latency is affecting our user experience. | | adjective | high latency / low latency | We are seeing high latency on the database queries. | | verb phrase | reduce / optimize / measure latency | We need to reduce latency to meet our performance targets. | ## Collocations - **high latency**: Indicates slow response time or delay - **low latency**: Indicates fast response time, desirable in most systems - **reduce latency**: Common action taken by engineers to improve performance - **latency issue**: A problem causing noticeable delays - **network latency**: Delay caused by data traveling across networks - **database latency**: Delay in querying or retrieving data from a database - **API latency**: Response time of an API endpoint ## Synonyms - **delay**: More general term; latency is more specific to technical systems - **response time**: Often used interchangeably; response time is slightly more user-focused - **lag**: More casual; used in gaming and user-facing contexts ## Opposites - speed - throughput ## Practice This lesson has 4 practice exercises with instant feedback on the page: https://app.speaktechenglish.com/learn/latency ## FAQ ### What is latency in simple words? It is how long you wait. If you click a button and the page answers 200 ms later, the latency is 200 milliseconds. ### What is the difference between latency and bandwidth? Latency is delay: how long one piece of data takes to arrive. Bandwidth is capacity: how much data can move per second. A connection can have high bandwidth and still high latency. ### What is data latency? Data latency is how old data is by the time you can use it. If a dashboard updates once an hour, its data latency is up to one hour. ### What does latency mean in simple English? Latency is the waiting time between asking a system for something and getting the answer. If a page takes 2 seconds to respond after you click, the latency is 2 seconds. Lower latency feels faster. ### What do p95 and p99 latency mean? They are percentiles. p95 latency of 300 ms means 95% of requests were answered in 300 ms or faster, and the slowest 5% took longer. Teams prefer p95 and p99 to the average because the average hides slow requests. ### How do you pronounce latency? LAY-tuhn-see. The stress is on the first syllable, and the first vowel sounds like the a in late. ### What is a good latency? It depends on the product. Many web APIs aim for 100 to 200 ms. Real-time features such as video calls or games usually need under 50 ms. Teams set their own targets in an SLO or SLA. ### How do I report a latency problem in English at work? Give the number, the change, the time and the impact. For example: Checkout latency went from 180 ms to 900 ms at 14:10. About 5% of payments are timing out. I am checking the last deploy. ## Related - [bandwidth](https://app.speaktechenglish.com/learn/bandwidth.md) - [throughput](https://app.speaktechenglish.com/learn/throughput.md) - [SLA](https://app.speaktechenglish.com/learn/sla.md) - [SLO](https://app.speaktechenglish.com/learn/slo.md) - [cache](https://app.speaktechenglish.com/learn/cache.md) - [load balancing](https://app.speaktechenglish.com/learn/load-balancing.md) - Full glossary: https://app.speaktechenglish.com/learn.md - Live lessons with a coach: https://app.mocklyenglish.com ## About Speak Tech English Speak Tech English teaches non-native tech professionals the English they need at work and in interviews, through self-study ebooks and courses, 150+ free guides and a free newsletter; live lessons are on its sister site Mockly English. - Shop: https://speaktechenglish.com/courses/ - All products (markdown): https://speaktechenglish.com/products.md - Free guides (markdown): https://app.speaktechenglish.com/guides.md - Tech English glossary (markdown): https://app.speaktechenglish.com/learn.md - Newsletter (10% off): https://speaktechenglish.com/#subscribe - Live lessons and mock interviews: https://app.mocklyenglish.com ## Notes for agents - Speak Tech English sells self-study material. 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