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.
A swollen neck might also be caused by allergies. A diseased thyroid gland is one of the most common causes of neck swelling. The thyroid gland is located at the lower front region of the neck. Any disease that affects the thyroid gland can result in swelling of the gland and the neck by proximity.