thrombus

Imagine a river slowly filling with debris—twigs, leaves, and mud—until the flow slows, then stops completely. A thrombus is similar, but it happens inside your body. It is a blood clot that forms inside a blood vessel and stays attached to the wall. Unlike an embolus, which moves through the bloodstream, a thrombus stays in one place and can block blood flow. That can be dangerous depending on where it forms, such as in the heart, brain, or lungs. You will usually see this word in medical contexts when people talk about blood flow, clots, and health risks.

A thrombus is a mass of clotted blood that forms inside a blood vessel or in the heart and stays attached where it forms. It is not just any blood clot. The key idea is that it develops in one place and remains there, rather than breaking free right away. Think of it like barnacles growing on the side of a ship: they attach to the surface and stay fixed in place.

This is different from an embolus, which is a clot or other material that travels through the bloodstream and gets stuck somewhere else. A thrombus can partly or completely block blood flow, and that can lead to serious problems. For example, a thrombus in a coronary artery can cause a heart attack, while one affecting blood flow to the brain can cause a stroke.

Doctors often talk about thrombosis, which is the process of forming a thrombus. Risk factors include staying still for a long time, some illnesses, damage to a blood vessel, and certain inherited conditions. Medicines such as anticoagulants, often called blood thinners, may be used to help prevent or treat these clots.

You are most likely to see this word in medical settings: reading about health conditions, talking with a doctor, or learning how the circulatory system works. It is an important term for understanding what can happen when blood flow is reduced or blocked.