Which of the following combining forms is not correctly matched with its meaning?

The combining form "pituitar/o" refers specifically to the pituitary gland, not the thyroid gland. The pituitary gland is often referred to as the "master gland" because it regulates other endocrine glands, including the thyroid gland. On the other hand, the combining form for the thyroid gland is "thyroid/o."

In contrast, the other options are correctly matched. "Pineal/o" accurately represents the pineal gland, which is involved in regulating sleep patterns and hormone production. "Phren/o" corresponds to the mind, often related to mental functions and conditions. Lastly, "pneum/o" is correctly associated with the lung, referring to conditions or processes related to the respiratory system. Thus, the second pairing stands out as inaccurate due to the different glands being referenced.