眼药水

• 目(eye)RADICAL
• 艮(hard; stop)PHONO-SEMANTIC

Two eyes looking straight ahead, stubborn and resolute like the character for "firm."

• 艹(grass; plant)RADICAL
• 约(promise; bind)PHONETIC

Medicine is made from grass and plants, sounding like "wish" or "promise".

• 水(water (pictographic))ASSOCIATIVE

Water mimics the flow of running water with ripples on both sides.