Since the "font" tag in HTML is being deprecated in HTML5 (and I understand why)
span tag would be the best way.
Although inline CSS is typically not recommended, here is an example:
<p> This is my <span style="font-weight:bold">paragraph</span>. </p>
div are similar, but the
div tag is a block element, so it will cause line-breaks.
span is an inline tag that can be used inline with your text.