Syntax | Terms | Equations | Horn formulas | Universal formulas | First-order formulas | Theories
A list of some first-order formulas.
| $R$ is a function | $\forall x\exists y(xRy)\mbox{ and }\forall x,y,z(xRy\mbox{ and }xRz\Longrightarrow y=z)$ |
| $f$ is onto | $\forall y\exists x(f(x)=y)$ |