Sentence:  : P \left ( B_1 \times B_2 \right ) = P \left ( B_1 \right ) P \left ( B_2 \right )    B_i \in \mathfrak{D} \left ( P_i \right ) ;i = 1, 2. / The probability space \left ( \Omega, P \right ) is called the <WSD>direct product</WSD> of \left ( \Omega_1, P_1 \right ) and \left ( \Omega_2, P_2 \right ), written / : \left ( \Omega, P \right ) = \left ( \Omega_1, P_1 \right ) \times \left ( \Omega_2, P_2 \right ). / For example, the Lebesgue measure on [0, 1]2 is the <WSD>direct product</WSD> of that on [0, 1] and itself. 
Meaning of the word marked with <WSD> tags:  Any of a number of mathematical objects analogously derived from a given ordered set of objects.