pawn, pawned article, pledge...

question, inquiry, enquiry

constitution (physical), physical make-up, predisposition (to disease)...

material, substance, matter

malicious, vicious, malignant...

hostage

quality (of a product or a service)

essence, true nature, substance...

nature (of a person), disposition, temperament...

question, interpellation

mass, quality and quantity

pawnshop

substance, essence, substantive...

disposition, temperament, nature...

makings (of), aptitude, talent...

quality of a fabric or cloth, texture of a fabric

simple, plain, modest...

characteristic, feature, special quality

water quality

protein

protein

substantial, real (as opposed to nominal)

protein

protein

qualitative

different (quality, nature), heterogeneous

nature, disposition, temperament...

good quality, fine quality, superior quality...

tone quality, sound quality

commitment, pledge, promise