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.
Some less common symptoms may include: 1  An enlarged thyroid gland (goiter). 2  Modest weight gain, often 10 lb (4.5 kg) or less. 3  Swelling of the arms, hands, legs, and feet, and facial puffiness, particularly around the eyes. 4  Hoarseness. Muscle aches and cramps.