You can “overwrite” a parent element’s language declaration by introducing any element apart from applet, base, basefont, br, frame, frameset, hr, iframe, meta, param, script (of HTML 4.0) with an own [lang](<https://www.w3.org/TR/html5/dom.html#the-lang-and-xml:lang-attributes>) attribute:

<p lang="en" title="An English paragraph">
    <span lang="de" title="A German sentence">Hallo Welt!</span>
</p>