Which condition is characterized by an increased tendency to form blood clots?

The condition characterized by an increased tendency to form blood clots is thrombus. A thrombus is a mass of blood constituents that forms within a blood vessel or the heart, leading to the obstruction of blood flow. This formation can occur due to various factors, including sluggish blood flow, increased coagulability, and changes in the vessel wall. When a thrombus forms improperly, it can lead to serious complications such as deep vein thrombosis or pulmonary embolism if it dislodges and travels to the lungs.

The other options describe different hematological issues. Thrombocytopenia refers to a low platelet count, which usually results in a decreased ability to form clots rather than an increased tendency. An embolus is a mass (like a clot, air bubble, or fat globule) that travels through the bloodstream and can block a vessel, but it’s typically not the condition that includes an increased risk of clot formation. Hemophilia A is a genetic disorder characterized by a deficiency of clotting factors, resulting in prolonged bleeding and a decreased ability to form stable clots. Thus, the nature of thrombus is directly linked to the propensity for excessive clot formation.