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For a more general overview encompassing other Indic scripts, see Kha (Indic).
Kha (ख) (खवर्ण khavarna) is the second consonant of the Devanagariabugida. It ultimately arose from the Brahmi letter 𑀔 (), after having gone through the Gupta letter . Letters that derive from it are the Gujarati letter ખ, and the Modi letter 𑘏.
Devanagari-using languages
In all languages, ख is pronounced as [kʰə] or [kʰ] when appropriate.
Certain words that have been borrowed from Persian and Arabic implement the nukta to more properly approximate the original word. It is then transliterated as a x.
Aryabhata used Devanagari letters for numbers, very similar to that of the Greeks, even after the invention of Indian numerals.
The values of the different forms of ख are:
Ifrah, Georges (2000). The Universal History of Numbers. From Prehistory to the Invention of the Computer. New York: John Wiley & Sons. pp. 447–450. ISBN0-471-39340-1.
Kurt Elfering: Die Mathematik des Aryabhata I. Text, Übersetzung aus dem Sanskrit und Kommentar. Wilhelm Fink Verlag, München, 1975, ISBN3-7705-1326-6
Georges Ifrah: The Universal History of Numbers. From Prehistory to the Invention of the Computer. John Wiley & Sons, New York, 2000, ISBN0-471-39340-1.
B. L. van der Waerden: Erwachende Wissenschaft. Ägyptische, babylonische und griechische Mathematik. Birkhäuser-Verlag, Basel Stuttgart, 1966, ISBN3-7643-0399-9
Fleet, J. F. (1911). "Aryabhata's System of Expressing Numbers". The Journal of the Royal Asiatic Society of Great Britain and Ireland. 43. Royal Asiatic Society of Great Britain and Ireland: 109–126. doi:10.1017/S0035869X00040995. JSTOR25189823.
), after having gone through the Gupta letter 
. Letters that derive from it are the Gujarati letter ખ, and the Modi letter 𑘏.