I believe they mean that the random variables have a common support. For example, if X ~ Unif[0,2] and Y ~ Unif[1,3], then their respective PDF's overlap in the interval [1,2], meaning the only interval where both X and Y can have common values is [1,2]. To illustrate, below is a representation of the supports of X and Y, below which is a representation of the real line.
1 Thyroid cancer is a malignant tumor of the thyroid gland. 2  Symptoms of thyroid cancer include swelling in the neck (goiter), neck pain, hoarseness, swallowing and breathing problem, swollen lymph gland in the neck.
People with thyroid cancer often experience the following symptoms or signs. Sometimes, people with thyroid cancer do not show any of these symptoms. Or, these symptoms may be caused by a medical condition that is not cancer. A lump in the front of the neck, near the Adam's apple. Hoarseness. Swollen glands in the neck. Difficulty swallowing. Difficulty breathing. Pain in the throat or neck. A cough that persists and is not caused by a cold. If you are concerned about one or more of the symptoms or signs on this list, please talk with your doctor.