Tabula recta
A tabula recta is a square table whose rows contain successively shifted versions of an alphabet.
Definition
A tabula recta is an alphabet square: the first row contains the alphabet, and each following row is cyclically shifted by one position. For an alphabet of n symbols, the table has n rows and columns.
Use in Vigenère
In a common convention, the key letter selects a row and the plaintext letter selects a column; their intersection gives the ciphertext letter. Decryption reverses that lookup. Equivalent tables may swap rows and columns without changing the underlying modular addition.
A tool, not a cipher
The table visualizes a family of Caesar shifts but does not define when each row is chosen. Vigenère, Beaufort, and Gronsfeld supply different key rules or arithmetic, so sharing a similar table does not make them the same cipher.
No. It is a lookup table; Vigenère also defines how a key selects shifts across the message.
No. It can be built for any ordered symbol set, with dimensions matching that set.