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== Features ==
[[File:Tachi and katana compared.jpg|thumb|right|Comparison between the [[Tang (tools)|tangs]] (nakago) of a {{lang|ja-Latn|katana}} (left) and {{lang|ja-Latn|tachi}} (right). The {{Nihongo|signature|銘|mei}} on the {{lang|ja-Latn|tachi}} tang was inscribed so it was always on the side of the tang facing outward as either sword was worn.]]

With a few exceptions, {{lang|ja-Latn|katana}} and {{lang|ja-Latn|tachi}} can be distinguished from each other, if signed, by the location of the signature ({{lang|ja-Latn|mei}}) on the [[Tang (tools)|tang]]. In general, the signature should be carved into the side of the tang facing outward as the sword is worn on the wielder's left waist. Since a {{lang|ja-Latn|tachi}} was worn cutting edge down, and the {{lang|ja-Latn|katana}} was worn cutting edge up, the {{lang|ja-Latn|mei}} would be in opposite locations on the tang of both types of swords.<ref>{{cite book|last1=土子|first1=民夫|last2=三品|first2=謙次|script-title=ja:日本刀21世紀への挑戦|url=https://books.google.com/books?id=BWy3gx-0PR8C|date=May 2002|publisher=Kodansha International|isbn=978-4-7700-2854-9 |page=30}}</ref>

An authentic {{lang|ja-Latn|tachi}} had an average cutting edge length ({{Transliteration|ja|nagasa}}) of {{convert|70|–|80|cm}}, and compared to a katana, was generally lighter in proportion to its length, had a greater taper from hilt to point, was more curved and had a smaller point area for penetrating heavy clothing.<ref>{{cite book|last=寒山|first=佐藤|author-link=寒山佐藤|title=The Japanese Sword|url=https://books.google.com/books?id=vFS2iT8QjqEC|year=1983|publisher=Kodansha International|isbn=978-0-87011-562-2 |page=15}}</ref>

Unlike the traditional manner of wearing the {{lang|ja-Latn|katana}}, the {{lang|ja-Latn|tachi}} was worn hung from the belt with the cutting edge down,<ref>Inami Hakusui (2009). ''Nippon-tô: the Japanese sword''. Cosmo. p. 160.</ref> and was most effective used by [[cavalry]].<ref>"A distinguished collection of arms and armor on permanent display", Issue 4 of ''Bulletin, Los Angeles County Museum of Natural History History Division'', Ward Ritchie Press, 1969. p. 120.</ref> Deviations from the average length of {{lang|ja-Latn|tachi}} have the prefixes ''ko-'' for "short" and ''ō-'' for "great, large" attached. For instance, {{lang|ja-Latn|tachi shōtō}} and closer in size to a {{lang|ja-Latn|[[wakizashi]]}} were called {{lang|ja-Latn|[[kodachi]]}}. The longest {{lang|ja-Latn|tachi}} (considered a 15th-century {{lang|ja-Latn|[[ōdachi]]}}) in existence is {{convert|3.7|m}} in total length with a {{convert|2.2|m}} blade, but is believed to be ceremonial. In the late 1500s and early 1600s, many {{lang|ja-Latn|tachi}} blades were modified into {{lang|ja-Latn|katana}}, their cut tangs ({{lang|ja-Latn|o-suriage}}) removing the smiths' signatures from the swords.<ref>Kōkan Nagayama (1998). ''The connoisseur's book of Japanese swords'', illustrated ed. Kodansha International. {{ISBN|4-7700-2071-6|978-4-7700-2071-0}}. p. 48.</ref>

For a sword to be worn in {{lang|ja-Latn|tachi}} style, it needed to be mounted in a {{lang|ja-Latn|tachi koshirae}}. The {{lang|ja-Latn|tachi koshirae}} has two hangers (ashi) so the sword can be worn in a horizontal position with the cutting edge down.<ref>Morihiro Ogawa and Kazutoshi Harada (2009). ''Art of the samurai: Japanese arms and armor, 1156–1868''. Metropolitan Museum of Art. {{ISBN|1-58839-345-3|978-1-58839-345-6}}. p. 193.</ref> A sword not mounted in a {{lang|ja-Latn|tachi koshirae}} could be worn {{lang|ja-Latn|tachi}} style by use of a {{lang|ja-Latn|koshiate}}, a leather device allowing any sword to be worn in the {{lang|ja-Latn|tachi}} style.<ref>Daniel C. Pauley (2009). ''Pauley's Guide - A Dictionary of Japanese Martial Arts and Culture''. Samantha Pauley. {{ISBN|0-615-23356-2|978-0-615-23356-7}}. p. 91.</ref>