A span is the distance measured by a human hand, from the tip of the thumb to the tip of the little finger. In ancient times, a span was considered to be half a cubit. Sometimes the distinction is made between the great span (thumb to little finger) and little span (thumb to index finger, or index finger to little finger).
Ancient Greek texts show that the span was used as a fixed measure in ancient Greece since at least archaic period. The word spithame (Greek: "σπιθαμή"), "span", is attested in the work of Herodotus in the 5th century BC; however, the span was used in Greece long before that, since the word trispithamos (Greek: "τρισπίθαμος"), "three spans long", occurs as early as the 8th century BC in Hesiod.
Size of the span
In Slavic languages, the analogue of the span is various words derived from Proto-Slavic *pędь (Bulgarian педя, Polish piędź, Russian пядь, Slovenian ped, etc.). In various Slavic languages it is the distance from the tip of the thumb to the tip of the little finger or index finger. For example, Slovenian velika ped = great span (23 cm), mala ped = little span (9.5 cm); Russian piad = 4 vershoks = 17.8 cm. See Obsolete Russian weights and measures.
In Hungarian, the span, or arasz, is occasionally used as an informal measure and occurs in two varieties: measured between the tips of the extended thumb and index finger, it is kis arasz (the "small arasz"); between the tips of the thumb and little finger, it is nagy arasz (the "large arasz"). The term "arasz," used by itself without a modifier, is usually understood as referring to the "large arasz," i.e., to the "span."
South Asian usage
In Bengali, it is called bighāt (বিঘত or বিঘৎ)
In Marathi, it is called “Weet” /वीत“.
In Malay, it is called "jengkal".
In Nepal, where this method of measurement is still used in informal context, a span is called Bhitta.
The span is commonly used as a traditional and informal measure in Mongolia, where it is called tuu (төө). Depending on the use of index or middle finger and the placement of the thumb, the span is named differently as tuu (төө) and mukhar tuu (мухар төө) etc.
The old Portuguese customary unit analogue to the span was the palmo de craveira or simply palmo.
- 1 palmo de craveira
- = 8 polegadas (Portuguese inches) 
- = 1/5 varas (Portuguese yards) 
- = 0.22 m
- Arthur Cornwallis Madan (1903). Swahili-English dictionary. Clarendon press. p. 78. Retrieved 27 January 2012.
- Edwin Pliny Seaver (1895). New Franklin arithmetic: Second book. Butler, Sheldon & co. p. 384. Retrieved 27 January 2012.
- Daniel O'Sullivan (1872). The principles of arithmetic. Thom. p. 69. Retrieved 27 January 2012.
- σπιθαμή, Henry George Liddell, Robert Scott, A Greek-English Lexicon, on Perseus Digital Library
- Herodotus, The Histories, 2.106, on Perseus Digital Library
- τρισπίθαμος, Henry George Liddell, Robert Scott, A Greek-English Lexicon, on Perseus Digital Library
- Hesiod, Works and Days, 426, on Perseus Digital Library
- Isaiah Steen (1846). A treatise on mental arithmetic, in theory and practice. p. 9. Retrieved 27 January 2012.
- Norman Lockyer, "Nature," Nature Publishing Group, Macmillan Journals Ltd., 1922.
- Emilio Achilles Monteverde (1861). Manual Encyclopedico para Uzo das Escolas de Instrucção Primaria. Imprensa Nacional, Lisboa.
- Lyle V. Jones. 1971. “The Nature of Measurement.” In: Robert L. Thorndike (ed.), Educational Measurement. 2nd ed. Washington, DC: American Council on Education, pp. 335–355.