= Solution
\b[<Pearlite> is a microstructural arrangement of two phases, <ferrite> and <cementite>, rather than a single phase.] <Ferrite> is an iron-rich <solid solution>; <cementite> is the carbide $\mathrm{Fe_3C}$. A <pearlite> colony contains alternating lamellae of these constituents formed by transformation of <austenite>.
A <thermodynamic phase> has a specified <crystal structure> and composition range with locally homogeneous properties on the appropriate scale. The word <pearlite> instead describes how distinct phases are arranged. Its lamellar spacing and orientation can change while the identities of its two phases remain the same.
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