Concept:
Morphine is an opioid analgesic used for severe pain.
Step 1: Analgesics are drugs that relieve pain.
Step 2: Morphine acts mainly on opioid receptors in the central nervous system.
Step 3: It decreases perception of pain and emotional response to pain.
Step 4: It is used in severe pain, such as postoperative pain or cancer pain.
Step 5: Therefore, morphine is used as a strong analgesic.
\[
\boxed{\text{Strong analgesic}}
\]