連接 conjunction

記号集合 $\Sigma$ 上で，${\bf L_{1}}$ と ${\bf L_{2}}$ を考えます．\[{\bf L_{1}}=\{x|x \in {\bf L_{1}}\}\]\[{\bf L_{2}}=\{y|y \in {\bf L_{2}}\}\]このとき，連接 ${\bf L_{1}}{\bf L_{2}}$ は，\[{\bf L_{1}}{\bf L_{2}}=\{xy | x \in {\bf L_{1}},y \in {\bf L_{2}} \}\]と定義されます．

Mathematics is the language with which God has written the universe.