---
tag: 1NNYWRN6B8
kind: concept
name: Sheffer stroke
aliases: [alternative-denial, inclusive-nand, logical-nand, nand-operator, scheffers-stroke, sheffer-connective, sheffers-stroke]
sources:
  - wikipedia: en:29388@r1375830657
    locator: Sheffer stroke
    note: adopted
    mention: wikipedia://en/29388
    sections: [Summary]
same_as:
  wikidata: Q3874243
  wikipedia: Sheffer stroke
inventory: [37N3PZJH03]
---

## Summary

In [[Boolean functions|0A58THH5XV]] and propositional calculus, the **Sheffer stroke** denotes a logical operation that is equivalent to the negation of the [[conjunction|025YZN3VJW]] operation, expressed in ordinary language as "not both". It is also called **non-conjunction**, **alternative denial** (since it says in effect that at least one of its operands is false), or **NAND** ("not and"). In digital electronics, it corresponds to the NAND gate. It is named after Henry Maurice Sheffer and written as $\mid$ or as $\uparrow$ or as $\overline{\wedge}$ or as $Dpq$ in Polish notation by Łukasiewicz (but not as ||, often used to represent [[disjunction|0F72FK8EKB]]).