speak up
No object
Talk more loudly, or say what you think
Could you speak up? I cannot hear you.
No object
Nothing follows the particle directly. You cannot say it with a direct object.
Related idiom
Read the meaning and origin of a related expression on The Village Idiom.
Practise it
Add it to your daily practice or see every verb with up.
Further reading: speak up on Wiktionary (CC BY-SA).