To communicate with one's voice, to say words out loud.
I was so surprised I couldn't speak.
To have a conversation.
It's been ages since we've spoken.
(by extension) To communicate or converse by some means other than orally, such as writing or facial expressions.
Actions speak louder than words.
To deliver a message to a group; to deliver a speech.
This evening I shall speak on the topic of correct English usage.
To be able to communicate in a language.
He speaks Mandarin fluently.
To utter.
I was so surprised that I couldn't speak a word.
To communicate (some fact or feeling); to bespeak, to indicate.
(sometimes humorous) To understand (as though it were a language).
So you can program in C. But do you speak C++?
To produce a sound; to sound.
Of a bird, to be able to vocally reproduce words or phrases from a human language.
To address; to accost; to speak to.