Tendon: The tissue by which a muscle attaches to bone. A tendon is somewhat flexible, but fibrous and tough. When a tendon becomes inflamed, the condition is referred to as tendinitis or tendonitis. Inflamed tendons are at risk for rupture.
Tendons are like ligaments in being tough, flexible cords. But tendons differ from ligaments in that tendons extend from muscle to bone whereas ligaments go from bone to bone as at a joint. Despite their tough fibrous nature, tendons and ligaments are both considered "soft tissue," that is soft as compared to cartilage or bone.
The term "tendon" comes from the Latin "tendere" and the Greek "teinein." Both mean "to stretch."
The Achilles tendon is a celebrated example of a tendon.
Tendinitis: Inflammation of a tendon (the tissue by which muscle attaches to bone). Tendinitis most commonly occurs as a result of injury, such as to the tendons around the shoulder or elbow. It can also occur as a result of an underlying inflammatory rheumatic disease, such as reactive arthritis or gout. Tendinitis is synonymous with tendonitis.