Change default "Posts" to "News" across WordPress admin - including all labels and the dashicon.

change-posts-to-news.php

<?php
/**
 * Change Posts to News.
 *
 * @author Amor Kumar (itsamoreh)
 */

/**
 * Change the dashboard menu labels.
 */
function change_post_label() {
	global $menu;
	global $submenu;
	$menu[5][0] = 'News';
	$submenu['edit.php'][5][0] = 'News';
	$submenu['edit.php'][10][0] = 'Add News';
	$submenu['edit.php'][16][0] = 'News Tags';
}

/**
 * Change the dashboard menu icon.
 */
function change_menu_icon() {
	global $menu;
	foreach ( $menu as $key => $val ) {
		if ( 'News' == $val[0] ) {
			$menu[$key][6] = 'dashicons-megaphone';
		}
	}
}

/**
 * Change the post object labels.
 */
function change_post_object() {
	global $wp_post_types;
	$labels = &$wp_post_types['post']->labels;
	$labels->name = 'News';
	$labels->singular_name = 'News';
	$labels->add_new = 'Add News';
	$labels->add_new_item = 'Add News Article';
	$labels->edit_item = 'Edit Article';
	$labels->new_item = 'New Article';
	$labels->view_item = 'View Article';
	$labels->search_items = 'Search News Articles';
	$labels->not_found = 'No Articles found';
	$labels->not_found_in_trash = 'No Articles found in Trash';
	$labels->parent_item_colon = 'Parent Articles:';
	$labels->all_items = 'All News';
	$labels->menu_name = 'News';
	$labels->archives = 'News Archives';
	$labels->attributes = 'News Attributes';
	$labels->insert_into_item = 'Insert into Article';
	$labels->uploaded_to_this_item = 'Uploaded to this Article';
	$labels->filter_items_list = 'Filter Articles List';
	$labels->items_list_navigation = 'Articles List Navigation';
	$labels->items_list = 'Articles List';
	$labels->item_published = 'Article published.';
	$labels->item_published_privately = 'Article published privately.';
	$labels->item_reverted_to_draft = 'Article reverted to draft.';
	$labels->item_scheduled = 'Article scheduled.';
	$labels->item_updated = 'Article updated.';
	$labels->item_link = 'Article Link';
	$labels->item_link_description = 'A link to an Article.';
	$labels->name_admin_bar = 'News';
}

add_action( 'admin_menu', __NAMESPACE__ . '\change_post_label' );
add_action( 'admin_menu', __NAMESPACE__ . '\change_menu_icon'  );
add_action( 'init', __NAMESPACE__ . '\change_post_object' );