Do the Imam and the congregants say "Amen" after reciting Al-Fatihah, and do they say it aloud or silently?

Firstly: The meaning of "Ameen" is "O Allah, answer [our prayer]," and whoever says it after a supplication is as if they have supplicated twice.

Secondly: It is sunnah (definition) for the individual praying alone and the congregant (ma'mum) to say "Ameen" after reciting Al-Fatihah. As for the Imam, the majority of scholars agree on the sunnah of his saying "Ameen" aloud, and authentic hadiths indicate this, such as the Prophet's (peace be upon him) saying: "When the Imam says Ameen, then say Ameen," and "The Messenger of Allah (peace be upon him) used to say Ameen."

Thirdly: Scholars differed regarding the congregant's saying "Ameen" aloud. Imam Abu Hanifa was of the opinion that it should be said silently, while Ash-Shafi'i, Ahmad, and some Malikis held that it should be said aloud, and this is the correct view. Hadiths and narrations from the Companions indicate this, such as the saying of Abu Hurairah (may Allah be pleased with him) that the Prophet (peace be upon him) used to raise his voice with "Ameen," and the narration of Ata' from Ibn Az-Zubair and those behind him, "until there was a clamor in the mosque." Nevertheless, this sunnah should not be a cause for discord and contention among Muslims.