seventh letter of the Greek alphabet
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Eta (uppercase/lowercase Η η) is a letter of the Greek alphabet. In very early Greek writing it stood for the consonant sound "h", but in Classical Greek it stood for a long vowel "e". In Modern Greek, it is pronounced as "i". In the system of Greek numerals, it has a value of 8. Letters that came from it include the Roman H and Cyrillic И.
In mathematics, the lowercase η is used to represent Dirichlet eta function. The same letter is also used to represent conformal time in cosmology, efficiency in telecommunications and elasticity in economics.
- ↑ "Greek/Hebrew/Latin-based Symbols in Mathematics". Math Vault. 2020-03-20. Retrieved 2020-10-06.
- ↑ "Eta Symbol in Greek Alphabet". www.greeksymbols.net. Retrieved 2020-10-06.