&quot;...calcify and ossify data structures and types...&quot;<p>What are you even talking about? This sounds like an assertion from someone who doesn&#x27;t use statically-typed languages and is just guessing.<p>To change a data structure in a statically-typed language, you change the declaration then fix any compile errors. It is easy in most cases.<p>In a dynamically-typed system, data structures actually get way <i>more</i> ossified, because when you change a structure you don&#x27;t really know what might be broken or when you are really done making the code correct again... Therefore programmers avoid this.