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.
Initially, though, people may go into the doctor because they notice the following symptoms and signs: 1  Lump in the Neck: Not all thyroid nodules are big enough to cause a noticeable lump. 2  Swollen Lymph Node: Swollen lymph nodes in the neck are another symptom of thyroid cancer (a symptom not related to thyroid nodules).