In Chamoru, Kai is a nativized version of the Spanish name Francisca, which is the feminine form of Francis, meaning "from France" or "free one".
In Mandarin Chinese, Kai is a common given name with one of several meanings, most often "victory" (凱), another being "open" (開). The word cài 菜 in Mandarin also means vegetable. Kai can also be used to transliterate the Chinese character used in some names meaning "start" (啟) in the Cantonese pronunciation.
In Hmong, Kai is a male name that is sometimes spelled Kha.
In Kono and Kissi, Kai is a male name; it is also a Paramount Chief title or prefix that means king of kings. It can be found as a name, or part of the names of several towns and regions in the Mano River Union Countries of Sierra Leone, Liberia and Côte d'Ivoire.
In Japanese, Kai has a number of meanings, including "ocean" (海), "shell" (貝), "restoration" and "recovery". As a surname, it means "Worth" (甲斐).
In Laotian, kai has numerous meanings, including "chicken", "to open" , "sick" , "egg" , or "to sell".
In Tamil, kai means "hand". With a longer 'a' sound, it would mean vegetable (காய்கறி)  which is interestingly similar to the Mandarin meaning of the same sound 'cài'.
In Thai, kai means "chicken" and used as a nickname.
In Wayuu, kai means "sun". It also means "the one who brings the light in the dawn" and/or "the one who brings knowledge".
In Welsh, Kai is a popular given name normally spelt "Cai". It is the diminutive of Cajus, meaning "Rejoicer", and is frequently used as an independent name in Wales due to its use in the Arthurian legend of Sir Kay. Another variation is Cae, meaning "pitch" or "field".
In Zambia, particularly in the Ngoni tribe of south central Africa, Kai is derived from the name Kaizala.
In Northern Ireland, data indicated that Kai experienced a significant rise in popularity as a male given name from 2002 to 2003. It has become popular in the UK, with many children born in the mid to late 1990s given the name. While it is typically a male given name, in recent years it has become popular for girls as well.