η

η

1. (mathematics) The metric tensor in quantum field theory.
2. (chemistry, physics) The coefficient of viscosity.
3. (engineering) Efficiency in engineering.
4. (physics) Sommerfeld parameter.
5. (machine learning) Learning rate.

• η on Wikipedia.Wikipedia

Derived from its majuscule counterpart Η, from the Phoenician letter 𐤇, heth.

η • (ē) (lowercase, uppercase Η)

1. Lower-case eta, the seventh letter of the ancient Greek alphabet. Its name was ἦτα and it represented a long open-mid front unrounded vowel: /ɛː/. It is often transliterated as either e or i. It is preceded by ζ and followed by θ.

• η' (i'), ,η (,i)
• h, H (Roman)
• и, И (Cyrillic)
• й, Й (Cyrillic)
• ⲏ, Ⲏ (Coptic)

• ἡ (hē, feminine article)
• ἥ (hḗ, feminine of pronoun ὅς)
• ᾖ (êi, inflectional form of verb εἰμί)
• (Greek-script letters) Α α, Β β, Γ γ, Δ δ, Ε ε, Ζ ζ, Η η, Θ θ, Ι ι, Κ κ, Λ λ, Μ μ, Ν ν, Ξ ξ, Ο ο, Π π, Ρ ρ, Σ σ ς, Τ τ, Υ υ, Φ φ, Χ χ, Ψ ψ, Ω ω
• (non-Classical letters) Ϝ ϝ, Ͷ ͷ, Ͱ ͱ, Ϻ ϻ, Ϙ ϙ, Ͳ ͳ
• (punctuation) · ;
• (diacritics) ᾿ ῾ ◌́ ◌̀ ῀ ¨

• IPA^(key): /i/ pronounced unstressed, together with its following word; compare to the stressed ή (í)
• Homophone: οι (oi)

From the vocalic usage of the Ancient Greek letter.

η • (i) (lowercase, uppercase Η)

1. Lower-case eta, the seventh letter of the modern Greek alphabet. Its name is ήτα and it represents a close front unrounded vowel: /i/. It is often transliterated as either e or i. It is preceded by ζ and followed by θ.

• (Greek-script letters) Α α, Β β, Γ γ, Δ δ, Ε ε, Ζ ζ, Η η, Θ θ, Ι ι, Κ κ, Λ λ, Μ μ, Ν ν, Ξ ξ, Ο ο, Π π, Ρ ρ, Σ σ ς, Τ τ, Υ υ, Φ φ, Χ χ, Ψ ψ, Ω ω
• (non-Classical letters) Ϝ ϝ, Ͷ ͷ, Ͱ ͱ, Ϻ ϻ, Ϙ ϙ, Ͳ ͳ
• (punctuation) · ;
• (diacritics) ᾿ ῾ ◌́ ◌̀ ῀ ¨

From Ancient Greek ἡ (hē).

η • (i) f sg

1. (definite) nominative feminine singular of ο (o) (the)