I want to TeX the Japanese characters 因子の部屋 (lit. "factor rooms"). How do I do that with LaTeX?
The simplest way with the pdflatex
engine is
\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{CJKutf8}
\begin{document}
\begin{CJK}{UTF8}{min}因子の部屋\end{CJK}
\end{document}
If you want an abbreviated command for typesetting Japanese fragments, then put this in the preamble
\newcommand{\textnihon}{\begin{CJK}{UTF8}{min}\nihon}
\newcommand{\nihon}[1]{#1\end{CJK}}
Now
\textnihon{因子の部屋}
will typeset the fragment.
Another way to cope with the problem is to switch to XeLaTeX or LuaLaTeX; with one of these engines, the document
\documentclass{article}
\usepackage{fontspec}
\newfontfamily{\nihon}{Hiragino Mincho Pro}
\newcommand{\textnihon}[1]{{\nihon#1}}
\begin{document}
This is a Japanese fragment: \textnihon{因子の部屋}
\end{document}
In place of "Hiragino Mincho Pro" you'll need to use a Japanese font present on your system.