Multiple excerpt lengths in wordpress
In WordPress, the length of the excerpt (the summary text displayed on the homepage or archive pages) can be controlled by the theme or by a plugin. The theme may have a specific setting for the excerpt length, or it may use the default WordPress excerpt length of 55 words. If a theme does not have a specific setting, you can use a plugin such as Advanced Excerpt to set the excerpt length. You can also customize the excerpt length by adding a function to the functions.php file of your theme.