The only time we come across the word ‘tribulation’ in the Bible is in Rev 7 : 14, when John the Apostle was told by one of the 24 elders : “These are they who came out of the great tribulation…” It is the translation of the Greek word ‘thlipsis’, which means trouble, distress, oppression, tribulation. But there are many other passages that refer to this period of time.
“There will be a time of distress such as not happened from the beginning of nations until then.” ( Dan 12 : 1 )
“For then there shall be great distress unequaled from the beginning of the world until now – and never to be equaled again.” ( Mt 24 : 21 )
“I will also keep you from the hour of trial that is going to come upon the whole world to test those who live on the earth.” ( Rev 3 : 10 ) etc.
So the word that is used in the book of Revelation to collectively address this period of time has been translated as ‘tribulation’.