This gist was "forked" from Eric Mann (https://gist.github.com/ericmann/5245768).

posts-to-articles.php

<?php

/**
 * Rename 'posts' to 'articles'
 */
function posts_to_articles( $translated ) {
	$words = array(
		// 'word to translate' = > 'translation'
		'Posts' => 'Articles',
		'Post'  => 'Article',
	);
 	
	$translated = str_ireplace(  array_keys( $words ),  $words,  $translated );
 	
	return $translated;
}
add_filter( 'gettext', 'posts_to_articles' );
add_filter( 'ngettext', 'posts_to_articles' );
add_filter( 'gettext_with_context', 'posts_to_articles' );