# TLS

Source: https://englishreference.com/word/tls
Updated: 2026-08-27

## Senses

### 1. internet security protocol

noun · CEFR C2 · Technical

Stands for Transport Layer Security. This is the system that encrypts data to keep your internet connection private and secure.

For teachers: Abbreviation for Transport Layer Security. A cryptographic protocol that provides end-to-end security for data sent between applications over the internet, succeeding the older SSL standard.

- The website uses TLS to make sure your credit card details stay private.
- Modern web browsers require a valid TLS certificate to establish a secure connection and prevent man-in-the-middle attacks.

Usage: Usually functions as an uncountable noun or as a modifier before another noun like 'certificate' or 'handshake'.

Teaching tip: While many people still say 'SSL', TLS is the modern technical standard that replaced it; in professional contexts, use TLS.

### 2. medical condition

noun · CEFR C2 · Technical

Stands for tumor lysis syndrome. A serious condition that can happen when cancer cells break down very quickly during treatment.

For teachers: Abbreviation for tumor lysis syndrome. A group of metabolic complications that can occur after treatment of cancer, where large amounts of tumor cells are killed off at once.

- The doctors monitored the patient closely for signs of TLS after the first round of chemotherapy.
- Prophylactic measures are essential for patients at high risk of developing TLS during the induction phase of treatment for aggressive lymphomas.

Usage: Uncountable noun; typically used in clinical or academic medical contexts.

Teaching tip: This is a highly specialized medical term; unless you are in the healthcare field, you will likely only encounter the internet security meaning of this acronym.

## Examples

- The website uses TLS to keep your login details safe.
- When you see a padlock icon in your browser's address bar, it usually means the connection is secured by TLS.
- Modern web browsers require the latest versions of TLS to ensure that data remains encrypted and protected against interception by unauthorized third parties.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.