<p>This paragraph is English, but the language is not specifically defined.</p>

<p lang="en-GB">This paragraph is defined as British English.</p>

<p lang="fr">Ce paragraphe est défini en français.</p>

.output {
    font: 1rem 'Fira Sans', sans-serif;
}

p::before {
    padding-right: 5px;
}

[lang="en-GB"]::before {
    content: '(In British English) ';
}

[lang="fr"]::before {
    content: '(In French) ';
}