Alternatives to writing greek letters. Write directly in greek letters

Question

When dealing with equations, I often end up writing a lot of mathematical symbols using greek letters. This makes the equations very long and a bit hard to read in my editor. Assuming I could write greek letters such as κ very quickly (without having to type \kappa to get κ) is there any way to have latex interpret κ as \kappa so I can still get the same output?

Answer 1

A standard way is to use an engine which accepts unicode letters. The following example compiles with LuaLaTeX:

\documentclass{article}

\usepackage{amsmath,fontspec,unicode-math}

\setmainfont{Stix}
\setmathfont{Stix}

\begin{document}
\noindent{}Α, α, Β, β/ϐ, Γ, γ, Δ, δ, Ε, ε/ϵ, Ζ, ζ, Η, η, Θ, θ/ϑ, Ι, ι, Κ, κ/ϰ, Λ, λ, Μ, μ, Ν, ν, \\
Ξ, ξ, Ο, ο, Π, π/, Ρ, ρ/ϱ, Σ, σ/ς, Τ, τ, Υ, υ, Φ, φ/ϕ, Χ, χ, Ψ, ψ, Ω, ω, \\
Ϝ, ϝ, Ϛ, ϛ, ϗ, Ϟ, ϟ, Ͱ, ͱ, Ͳ, ͳ, Ϳ, ϳ, Ϡ, ϡ, Ϸ, ϸ, Ϲ, ϲ, Ϻ, ϻ. 

\begin{align*}
&Α, α, Β, β/ϐ, Γ, γ, Δ, δ, Ε, ε/ϵ, Ζ, ζ, Η, η, Θ, θ/ϑ, Ι, ι, Κ, κ/ϰ, Λ, λ, Μ, μ, Ν, ν, \\
& Ξ, ξ, Ο, ο, Π, π/, Ρ, ρ/ϱ, Σ, σ/ς, Τ, τ, Υ, υ, Φ, φ/ϕ, Χ, χ, Ψ, ψ, Ω, ω, \\
& Ϝ, ϝ, Ϛ, ϛ, ϗ, Ϟ, ϟ, Ͱ, ͱ, Ͳ, ͳ, Ϳ, ϳ, Ϡ, ϡ, Ϸ, ϸ, Ϲ, ϲ, Ϻ, ϻ. 
\end{align*}
Do note confuse ϟ (rather unknown glyph) with ᛋ (infamous rune).
\end{document}

I included some more obscure Greek letters just for comparison.

Yous should chose a typeface with math support when using this approach. I recommend an OTF typeface. A list of such typefaces is found on http://www.tug.dk/FontCatalogue/mathfonts.html. You should also consult the fine manuals of the packages used in the example.

Another fine engine is XeLaTeX.