1. related to embryo or undeveloped.   ciliated   embryonic   immune   igneous   Hint Half-n-half Clue   2. leading to absence of pain.   analgesic   homogeneous   impermeable   horticultural   Half-n-half Clue   3. tending to a center.   diurnal   centripetal   aromatic   congenital   Half-n-half Clue   4. existing from birth.   congenital   acrid   dorsal   integral   Half-n-half Clue   5. inactive or lacking power of action.   congruent   inert   congenital   astronomical   Half-n-half Clue   6. arranged in gradations (e.g., of difficulty).   ductile   concave   embryonic   graduated   Half-n-half Clue   7. distinct or unconnected.   acrid   discrete   incandescent   determinate   Half-n-half Clue