Step 1: Compare their behaviour in a field. Put a rod of each material in a magnetic field. A paramagnetic rod turns to align along the field and moves toward the stronger-field region (weak attraction). A diamagnetic rod sets itself across (perpendicular to) the field and moves toward the weaker-field region (weak repulsion).
Step 2: Compare susceptibility and permeability. For paramagnetics the susceptibility is small and positive (\(0 < \chi \ll 1\)) and relative permeability \(\mu_r > 1\). For diamagnetics the susceptibility is small and negative (\(-1 < \chi < 0\)) and \(\mu_r < 1\).
Step 3: Compare the atomic origin. Paramagnetism arises because each atom already has a permanent magnetic dipole moment that partly aligns with the field. Diamagnetism arises in atoms with zero net moment; the applied field induces a tiny opposing moment (Lenz-law style). Paramagnetism also weakens with rising temperature, while diamagnetism is essentially temperature independent.
\[\boxed{\text{Para = permanent moments, attracted; Dia = no moment, repelled}}\]