Final answer:
All Athenian male citizens over the age of 18 participated in the Assembly, which had the authority to pass laws and make decisions on war and elections in Athens' direct democratic system, though it excluded women, slaves, and non-citizens.
Step-by-step explanation:
In Athens, all male citizens over 18 years old made up the assembly which passed all laws, elected officials, and made decisions on war.
Athenian democracy was a system of direct democracy, differing from modern representative systems. Every male citizen, specifically those who were not slaves, women, or foreign residents, had the right to participate in the governmental process, including sitting in the Assembly.
Participation in the Assembly imbued immense political power, from creating legislation to making critical decisions such as declaring war.
Yet, it should be noted that by contemporary standards, this was not a fully inclusive or equal system, as only males with Athenian citizenship were afforded these rights, excluding the majority of the population.