Notation, First Definitions 转 http://brnt.eu/phd/node9.html

LaTeX command	Equivalent to	Output style	Remarks
\textnormal{...}	{\normalfont...}	document font family	This is the default or normal font.
\emph{...}	{\em ...}	emphasis	Typically italics. Using emph{} inside of italic text removes the italics on the emphasized text.
\textrm{...}	{\rmfamily...}	roman font family
\textsf{...}	{\sffamily ...}	sans serif font family	Matrix
\texttt{...}	{\ttfamily ...}	teletypefont family	This is a fixed-width or monospace font.
\textup{...}	{\upshape...}	upright shape	The same as the normal typeface.
\textit{...}	{\itshape ...}	italic shape
\textsl{...}	{\slshape ...}	slanted shape	A skewed version of the normal typeface (similar to, but slightly different from, italics).
\textsc{...}	{\scshape ...}	Small Capitals
\uppercase{...}		UPPERCASE (ALL CAPS)	Also \lowercase. There are some caveats, though; seehere.
\textbf{...}	{\bfseries ...}	bold	vector
\textmd{...}	{\mdseries...}	medium weight	A font weight in between normal and bold.
\textlf{...}	{\lfseries ...}	light	A font weight lighter than normal. Not supported by all typefaces.