'Tribulation' in the Bible

and they have no root in themselves, but endure for a while; then, when tribulation or persecution ariseth because of the word, straightway they stumble.

For those days shall be tribulation, such as there hath not been the like from the beginning of the creation which God created until now, and never shall be.

But in those days, after that tribulation, the sun shall be darkened, and the moon shall not give her light,