Fitna comes from an Arabic word which means to seduce, tempt or lure away. In modern usage, it is used to describe forces that cause controversy fragmentation, scandal, chaos, or discord within the Muslim community. 
“The Arabic word fitnah includes meanings of testing and trial. The root is taken from the phrase fatantu al-fiddah wa’l-dhahab (I assayed (tested the quality of) the silver and gold), meaning I melted the metals to separate the bad from the good. Similarly, Allah سبحانه و تعالىsays in the Qur’an (interpretation of the meaning): ‘(It will be) a Day when they will be tried [yuftanoona] (punished, i.e. burnt) over the Fire!’ Quran.Surah Dhaariyaat 51:13, meaning, burning them with fire.” Tahdheeb Al-Lughah, 14:196.
1- Testing and trial, as in the aayah (interpretation of the meaning):
“Do people think that they will be left alone because they say: ‘We believe, and will not be tested [la yuftanoon]” Qur’an.Surah Ankaboot 29:2.
i.e., that they will not be subjected to trial, as Ibn Jareer رضي الله عنهsaid.
2- Blocking the way and turning people away, as in the aayah (interpretation of the meaning):
“but beware of them lest they turn you [yaftinooka] (O Muhammad ﷺ) far away from some of that which Allah سبحانه و تعالىhas sent down to you” Qur’an.Surah Ma’idah 5:49.
Al-Qurtubi رحمت اللهsaid: this means blocking your way and turning you away.
3- Persecution, as in the aayah (interpretation of the meaning):
“Then, verily, your Lord for those who emigrated after they had been put to trials [futinoo] and thereafter strove hard and fought (for the Cause of Allah سبحانه و تعالى) and were patient, verily, your Lord afterward is, Oft‑Forgiving, Most Merciful” Qur’an.Surah Nahl 16:110.
Put to trial means persecuted.
“And fight them until there is no more Fitnah (disbelief and worshipping of others along with Allah سبحانه و تعالى)” Qur’an.Surah Baqarah 2:193.
5- Falling into sin and hypocrisy, as in the aayah (interpretation of the meaning):
“(The hypocrites) will call the believers: “Were we not with you?” The believers will reply: “Yes! But you led yourselves into temptations [fatantum anfusakum], you looked forward for our destruction; you doubted (in Faith) and you were deceived by false desires” Qur’an.Surah Hadeed 57:14.
6- Confusing truth with falsehood, as in the aayah (interpretation of the meaning):
“And those who disbelieve are allies of one another, (and) if you (Muslims of the whole world collectively) do not do so [i.e. become allies, as one united block under one Khaleefah (a chief Muslim ruler for the whole Muslim world) to make victorious Allah’s سبحانه و تعالىreligion of Islamic Monotheism], there will be Fitnah (wars, battles, polytheism) and oppression on the earth, and a great mischief and corruption (appearance of polytheism)”Qur’an.Surah Anfaal 6:73.
7- Misguidance, as in the aayah (interpretation of the meaning):
“And whomsoever Allaah سبحانه و تعالىwants to put in Al‑Fitnah (error, because of his rejecting of Faith), you can do nothing for him against Allaah” Qur’an.Surah Al-Maa'idah 5:41.
The meaning of fitnah here is misguidance. Al-Bahr Al-Muheet 4/262 by Abu Hayaan رحمت الله,
The Prophet ﷺused to pray: "Allahumma inni a'udhu bika min fitnatin-nari, wa 'adhabin-nari, wa min sharril-ghina wal-faqri (O Allah سبحانه و تعالى! I seek refuge in You from the trials and the torment of the Fire and from the evils of wealth and poverty)." Sahih Al-Muslim H:2078
Ibn al-Qayyim رحمت اللهsaid:
With regard to the “fitnah” which Allah سبحانه و تعالىattributes to Himself or which His Messenger ﷺattributes to Him, as in the aayah (interpretation of the meaning), ‘Thus We have tried [fatannaa] some of them with others’ [Quran.Surah Al-An’aam 6:53] and the words of Moosa عليه السلام‘It is only Your trial [fitnatuka] by which You lead astray whom You will’ [Qur’an.Saurah al-A’raaf 7:155] – interpretation of the meaning], that carries a different meaning, which is a test or trial from Allah سبحانه و تعالىto His slaves by means of good things and bad, blessings and calamities. This is one thing; the fitnah of the mushrikeen is another thing; the fitnah or trial of the believer by means of his wealth, children and neighbour is another thing. 
The general of the trials and tribulations (fitna) which have occured : the greatest of their reason is a decrease of Patience.
And as such : Fitna has two reasons:
1. Weakness of knowledge or
2. Weakness of Patience
Indeed ignorance and transgression are the causes of evil.
Ibn Muflih رحمت اللهsaid in "Al-Fur'oo : 6/160-161"