Giving an excerpt a unique class can come in handy when writing CSS in the BEM style. Here's a small function to do that.
This goes into your function.php file:
function cm_excerpt( $class ) {
$excerpt = strip_tags( get_the_excerpt() );
echo '<p class="' . $class . '">' . $excerpt . '</p>';
}Usage:
<?php excerpt('article__excerpt'); ?>