The common values for font series are (taken from fntguide):
m Medium
b Bold
bx Bold extended
sb Semi-bold
c Condensed
m is the default font weight, bx is the default bold series. The c and sb weights do not exist in Computer Modern and Latin Modern. But it is a little known fact that the nonextended bold series, b, is also available for the roman family in these fonts.
You would switch to this series with
\fontseries{b}\selectfont Text…
and make it the default bold series (such that it affects \bfseries and \textbf) with
\renewcommand{\bfdefault}{b}
However, there is no similar font weight defined for the sans serif CM/LM font family.
Fortunately, Latin Modern comes to rescue with its Latin Modern Sans Demi Cond font, available in regular and oblique shapes. This font is somewhat more dense than the normal one, but because of that it also looks heavier. You can access this font through the sbc font weight, which can be used just as b above. If you use XeLaTeX or LuaLaTeX, you can also select this font by name with fontspec.
And to show all the fonts:

\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\newcommand{\test}[2]{%
\makebox[2.5cm][l]{#2:} {\fontseries{#1}\selectfont The quick brown fox\dots}\par}
\begin{document}
Roman font family:
\test{m} {Medium}
\test{b} {Bold}
\test{bx} {Bold extended}
\null\par
\sffamily
Sans serif font family:
\test{m} {Medium}
\test{sbc}{Sans Demi Cond}
\test{bx} {Bold extended}
\end{document}
If you use a font other than Computer Modern or Latin Modern, you can check for the font weights mentioned before or examine the list of font files/font documentation.
fontseriestosemibold. As\bfis an deprecated command (use\textbfinstead), try something like:\newcommand{\sebo}[1]{{\fontseries{sb}#1}}, but close to none fonts supportsemibold– Tom Bombadil Sep 08 '11 at 09:55\selectfontafter\fontseries. – Andrey Vihrov Sep 08 '11 at 15:35BoldFont={* Semiold}as a font option when using XeLaTeX. – caw Dec 02 '14 at 04:59\resizebox{15mm}{!}{\Large word}. This is in the context of a larger font size (characters are drawn with slimmer strokes). It works by using a smaller font size and then scaling it up to match the larger size. (That15mmneeds to be adjusted depending on the word.) – Evgeni Sergeev Feb 07 '17 at 04:35\newcommand\sbseries{\fontseries{sb}\selectfont}and\DeclareTextFontCommand\textsb{\sbseries}. To replace bold with semibold in the entire document, you can redefine\renewcommand\bfdefault{sb}(if asbseries exists). Many font packages also support an option such as[sbdefault]. – Davislor Apr 30 '21 at 07:36