Over an algebraically closed field $k$ of characteristic zero, there is a bijection
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\begin{align*}
\{\text{finite-dimensional semisimple Lie algebras over } k\}/\cong
&\longleftrightarrow
\{\text{finite disjoint unions of finite type Dynkin diagrams}\}/\cong .
\end{align*}
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Under this bijection, the zero Lie algebra corresponds to the empty diagram, and nonzero simple Lie algebras correspond exactly to connected finite type Dynkin diagrams.