Who could vote in ancient Athens, and what was ostracism?

In Athens, every adult male citizen could vote, and that was at most about three adults in ten. Participation was open to free, adult male citizens, which excluded minors, metics (foreign residents), women and slaves. Adult male citizens probably made up no more than 30 percent of the adult population. Within that group the democracy was direct: there were no representatives, and any citizen over 20 could take part in the assembly, and it was a duty to do so.

The voting itself was a hands-on affair. Citizens usually voted by raising their hands while officials judged the result by sight. In the 5th century, public slaves even herded citizens into the meeting place with a red-stained rope, fining those who got red on their clothes.

Athens also had a safeguard against someone growing too powerful: ostracism. Once a year the assembly was asked whether to hold one. Any citizen could be expelled from Athens for ten years. Voters wrote a name on a broken piece of pottery, an ostrakon, which gave us the word. The banished man kept his property and his status. Ostracism was often used preemptively against someone thought to be a threat to the state or a potential tyrant.

So the first democracy was both broad and narrow: remarkable for its direct voting, and limited to a minority of the people who lived there.