These are common terminology in Forth and other computer languages with a stack.

`peek`

or `tos`

- Examine top of stack. (
*... x y* `tos` gives you *y* and keeps the stack)
`push`

- Add element to top of stack; other elements are
*pushed* down. (*... x* `push y` makes the stack *... x y*)
`pop`

- Remove element from top of stack. (
* ... x y* `pop` makes the stack *... x*)
`swap`

- Swap top two stack elements. (
*... x y* `swap` makes the stack *... y x*)
`rot`

- "Rotate" top 3 elements, bringing third element to top of stack. (
*... x y z* `rot` makes the stack *... y z x*)
`unrot`

- "Rotate" top 3 elements in other direction. (
*... x y z* `unrot` makes the stack *... z x y*)
`dup`

- Duplicate top stack element. (
*... x* `dup` makes the stack *... x x*)
`over`

- Duplicate second stack element over top of stack. (
*... x y* `over` makes the stack *... x y x*; equivalent to `swap dup unrot`)
`nip, tuck, pick, ...`

- Over the years, Forth programmers invented many more useful operations!