= Relative constructible universe
{title2=$L(A)$}
For a <transitive set> $X$, the relative constructible universe $L(X)$ is the union of the <relative constructible hierarchy>, starting at $L_0(X)=X$, applying the <definable power set> at successors and taking unions at <limit ordinals>. It is the smallest <inner model> of <ZF> containing $X$ and all its members. For an arbitrary <set> $A$, take the base $X$ to be the <transitive closure> of $\{A\}$, so that $A\in X$. <Axiom of choice> need not hold for an arbitrary base; the construction uses initial parameters rather than a predicate relativization.
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