Qualitative: refers to observations or statements of general quality or trend, without specifing any numerical values.  The opposite of quantitative.

Quantitative: refers to observations or statements that specify measured numerical values.  The opposite of qualitative.

Quantum mechanics: the treatment of matter as undergoing quantized energy changes.  In quantum mechanics, small particles do not behave in the same way as large particles do.  For example, the electrons in an atom cannot be described as small particles, but are instead waves.