η

See also: ή, ἡ, ἥ, ᾖ, -η, դ, ղ, Ⴂ, and Appendix:Variations of "h"

η U+03B7, η GREEK SMALL LETTER ETA ← ζ [U+03B6] Greek and Coptic θ → [U+03B8]

𝜂 U+1D702, 𝜂 MATHEMATICAL ITALIC SMALL ETA ← 𝜁 [U+1D701] Mathematical Alphanumeric Symbols 𝜃 → [U+1D703]

Translingual

Symbol

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.

See also

• η on Wikipedia.Wikipedia

Ancient Greek

Etymology

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

Letter

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.

Derived terms

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

See also

• 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) ᾿ ῾ ◌́ ◌̀ ῀ ¨

Greek

Pronunciation

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

Etymology 1

From the vocalic usage of the Ancient Greek letter.

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.

See also

• (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) ᾿ ῾ ◌́ ◌̀ ῀ ¨

Etymology 2

From Ancient Greek ἡ (hē).

Article

η • (i) f sg

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

Declension

The definite article

number	singular			plural
gender	m	f	n	m	f	n
nominative	ο	η	το	οι	οι	τα
genitive	του	της	του	των	των	των
accusative	το(ν)*	τη(ν)*	το	τους	τις	τα
* The final "ν" is preserved before vowels, and the plosive/affricate consonants:       κ, π, τ, ξ, ψ, μπ, ντ, γκ, τσ, τζ 1. Archaic forms used in certain fixed phrases:       τοις (tois), τας (tas)