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.
In many cases, there are no symptoms (asymptomatic) associated with thyroid cancer. Pain in the neck, hoarseness and swollen lymph nodes especially in the neck may be present in some cases. Although thyroid cancer is relatively uncommon, it is the most common form of cancer affecting the endocrine system.