[Math] What does $\forall$ mean notation ProofWiki What does the upside-down A on this page mean? $$\forall a,b\in S: a\circ x=b\circ x \implies a=b$$ Best Answer The symbol $\forall$ means "for all." The symbol $\in$ means "in" or is an element of. In your context, it means for all $a$ and $b$ in $S$. Related Solutions[Math] the meaning of the math symbol $\because$ The inverted form of the therefore sign ( $\therefore$ ) used in proofs before logical consequences, is known as the because sign ( $\because$ ) and it is used in proofs before reasoning. Related Question
Best Answer
The symbol $\forall$ means "for all." The symbol $\in$ means "in" or is an element of.
In your context, it means for all $a$ and $b$ in $S$.