= Solution
A <molecule> is an electrically neutral bound assembly of more than one <atom>. It can contain identical atoms, as in $\mathrm O_2$, or different atoms, as in $\mathrm H_2O$. Discrete molecules are not a universal description of matter: an extended ionic crystal does not consist of separate neutral molecules corresponding to each empirical formula unit. The IUPAC definition also specifies binding sufficient to support a vibrational state.<IUPAC Compendium of Chemical Terminology (Gold Book) by International Union of Pure and Applied Chemistry/Molecule in the IUPAC Gold Book>[Definition M04002]{ref}
<Elasticity> is a body's tendency to recover its original configuration when the deforming <force> is removed. Within a linear regime, <Hooke's law> makes <stress> proportional to <strain>, but elasticity does not require exact linearity. The <elastic limit> matters: permanent <plastic deformation> is a different response.
<Inertia> is the property expressed by <Newton's first law>: without a resultant external <force>, a body's <velocity> remains constant in an <inertial frame of reference>. <Mass> measures translational inertia. It is not a force acting against motion, and a moving body does not require a continuing forward force merely to keep moving.
A <force> describes an interaction that changes <momentum>. In <Newtonian mechanics>,
$$
\boxed{\mathbf F_{\rm resultant}=\frac{d\mathbf p}{dt};\qquad
\mathbf F_{\rm resultant}=m\mathbf a\quad\text{for constant }m.}
$$
A force has magnitude and direction; its point of application also matters for the <torque> and hence the body's rotational response.
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