The impeachment trial of President Donald Trump is set to get underway in the US Senate today.
Mr Trump is the third president in his country’s history to face such proceedings, in which senators will judge whether or not he has committed the charge he is accused of.
If he is found guilty, he could be removed from office.
Here is everything you need to know:
What is impeachment?
Impeachment is a way of holding senior government figures to account. A president can be impeached for committing offences such as treason and bribery or other “high crimes and misdemeanours”.
Congress first votes on whether there is a case against the accused, and then a trial takes place in the upper house, known as the Senate.
Why is the trial taking place?
A transcript of a phone call between Mr Trump and Mr Zelenskiy
In August last year a whistleblower made allegations against Mr Trump and, following an investigation, Democrats in the US House of Representatives voted to impeach him in December.
He faces two charges – abuse of power and obstruction of congress.
The first charge accuses the president of attempting to get a foreign government to help him to hold his office in the upcoming presidential election.
To do this, he allegedly withheld US military aid to Ukraine to tempt the country’s president Volodymyr Zelenskiy to investigate his democratic rival Joe Biden.
Secondly, Mr Trump is accused of obstructing Congress by refusing to comply with their investigation. The president has always denied any wrongdoing.
What happens next?
Nancy Pelosi, speaker of the house of representatives
The trial begins with four days of opening arguments, with a maximum of 24 hours per side.
Senators then have up to 16 hours to question the prosecution and defence, followed by four hours of debate.
After that, they may vote to call more witnesses.
According to Senate rules, the trial must proceed every day, except Sunday, until it is resolved.
There are 100 senators, with Mr Trump’s Republican Party currently holding a majority of 53.
For almost all of the decisions during the trial, 51 senators must agree.
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