Iranians chant in support of defeated presidential candidate Mir Hossein Mousavi
Iranians are marking University Student Day, traditionally an anti-US event that commemorates the killing of three students in 1953. Opposition supporters are expected to try to hijack official protests by chanting their own anti-government slogans.
Olivia Cornes navigates some of the opposition chants heard in Iran since June's disputed presidential elections, with the help of BBCPersian.com and protesters themselves.
The waves of street chanting among anti-regime protesters are spontaneous but many are not new.
Slogans that Iranians used 30 years ago to call for an end to the Shah's regime are now thrown back at the Islamic regime which replaced it.
There are terrible class differences in Iran, this plays a part in the protests
In some cases, "Allahu Akbar" (Eng: God is great) or "Marg bar dictator" (Eng: Death to the dictator) - the chants have not changed at all.
The night-time cries of "Allahu Akbar" from people's rooftops continued for months in the early stages of the revolution which overthrew the Shah.
The current Islamic government sees the same chant as a threat.
Rooftop protests heard at the height of the unrest in June and July stopped after Basiji forces started patrolling at night, marking the buildings where the chant could be heard above.
Arrests would be made the next day.
Parvaneh, a student and opposition supporter in Tehran, told the BBC the chants had become more personal and focused.
Protesters shout 'Death to you', meaning president Ahmadinejad, at end of chant
"Shortly after the election the chants were only about people getting their votes back, but now it is more about the system and leaders themselves."
Revolutionary chants have been reworked, with a crucial name change.
One of the big anti-Shah chants ended with the slogan "Death to Shah!".
The same chant can be heard now, dedicated to Iranian President Mahmoud Ahmadinejad: "Ahmadi you traitor, may you be turned out of your country. You ruined our land... Death to you, death to you, death to you, death to you!"
Some Iranians say they were shocked when they heard current leaders publicly insulted for the first time.
One chant goes much further back than 1979.
President Ahmadinejad's early dismissal of those who questioned his re-election as "dirt and dust" prompted an adaptation of a poem by the 13th-Century Persian philosopher Rumi: "You are the tumbleweed and dust... You are the enemy of the land."
One chant - a new one - which attacks Supreme Leader Ayatollah Ali Khamenei personally, has the rhyme "Khamenei ghatele, Velayatesh batele" - "Khamenei is a murderer, his leadership is invalid".
Opposition chant naming supreme leader Ayatollah Khamenei
Another way the old chants are being reworked is to emphasise Iranian identity over Islamic identity.
A main revolutionary cry was: "Estaghlal, Azadi, Jomhuriye Eslami" (Eng: Independence, Freedom, Islamic Republic).
This suggested an Islamic Republic could bring freedom from the state oppression of the Western-backed Shah's regime. In 1979, Ayatollah Khomenei said Iran needed to return to Islamic values and cleanse itself of what he termed "Westoxification".
Today's protesters, largely young city-dwellers, have inverted the chant to "Estaghlal, Azadi, Jomhuriye Irani" (Eng: Independence, Freedom, Iranian Republic).
It is an appeal for a secular state and also for the freedoms people hoped they were going to get the first time the chant was used.
Tehran student Behrooz notes a chant he heard for the first time on 4 November, distancing Iranians from Islam even further: "Nejade ma aryast-deen, az siasat jodas" (Eng: We are an Aryan race, religion and politics don't mix).
The chant harks back to a pre-Islamic Iran.
Ayatollah Khomenei's traditional day of support for Palestinians, Quds day, in September, was used by opposition demonstrators to complain that the regime cared more about others than its own people.
They could be heard chanting "Na Gaza, na Lebnan, jaanam fadaaye Iran" (Eng: Not Gaza nor Lebanon, I give my life for Iran).
Opposition crowds in Isfahan chant 'Not Gaza, not Lebanon, I will die for Iran'
Another student in Tehran, Siavash, told the BBC he thought the biggest test for the opposition demonstrators was coming soon.
Ten days of traditional Shia mourning rituals, known as Muharram, begin in mid-December.
"We will go out and chant 'Ya Hossein, Mir Hossein', " he said.
"Ya Hossein" refers to the imam who was martyred in Karbala in 680 AD and "Mir Hossein" is, of course, the opposition leader.
"This way, we convert the religious chant into a political one," said Siavash.
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