The Quran root ي ق ن y-q-n

وَالَّذِينَ يُؤْمِنُونَ بِمَا أُنزِلَ إِلَيْكَ وَمَا أُنزِلَ مِن قَبْلِكَ وَبِالْآخِرَةِ هُمْ يُوقِنُونَ ٤

يُوقِنُونَ yūqinūna · firmly believe

And who believe in what has been revealed to you, [O Muḥammad], and what was revealed before you, and of the Hereafter they are certain [in faith]. (Surah Al-Baqarah, 2:4)

وَقَالَ الَّذِينَ لَا يَعْلَمُونَ لَوْلَا يُكَلِّمُنَا اللَّهُ أَوْ تَأْتِينَا آيَةٌ كَذَٰلِكَ قَالَ الَّذِينَ مِن قَبْلِهِم مِّثْلَ قَوْلِهِمْ تَشَابَهَتْ قُلُوبُهُمْ قَدْ بَيَّنَّا الْآيَاتِ لِقَوْمٍ يُوقِنُونَ ١١٨

يُوقِنُونَ yūqinūna · (who) firmly believe

Those who do not know say, "Why does Allāh not speak to us or there come to us a sign?" Thus spoke those before them like their words. Their hearts resemble each other. We have shown clearly the signs to a people who are certain [in faith]. (Surah Al-Baqarah, 2:118)

وَقَوْلِهِمْ إِنَّا قَتَلْنَا الْمَسِيحَ عِيسَى ابْنَ مَرْيَمَ رَسُولَ اللَّهِ وَمَا قَتَلُوهُ وَمَا صَلَبُوهُ وَلَٰكِن شُبِّهَ لَهُمْ وَإِنَّ الَّذِينَ اخْتَلَفُوا فِيهِ لَفِي شَكٍّ مِّنْهُ مَا لَهُم بِهِ مِنْ عِلْمٍ إِلَّا اتِّبَاعَ الظَّنِّ وَمَا قَتَلُوهُ يَقِينًا ١٥٧

يَقِينًا yaqīnan · certainly

And [for] their saying, "Indeed, we have killed the Messiah, Jesus the son of Mary, the messenger of Allāh." And they did not kill him, nor did they crucify him; but [another] was made to resemble him to them. And indeed, those who differ over it are in doubt about it. They have no knowledge of it except the following of assumption. And they did not kill him, for certain. (Surah An-Nisa, 4:157)

وَكَذَٰلِكَ نُرِي إِبْرَاهِيمَ مَلَكُوتَ السَّمَاوَاتِ وَالْأَرْضِ وَلِيَكُونَ مِنَ الْمُوقِنِينَ ٧٥

الْمُوقِنِينَ l-mūqinīna · the ones who are certain

And thus did We show Abraham the realm of the heavens and the earth that he would be among the certain [in faith]. (Surah Al-An'am, 6:75)

وَجَحَدُوا بِهَا وَاسْتَيْقَنَتْهَا أَنفُسُهُمْ ظُلْمًا وَعُلُوًّا فَانظُرْ كَيْفَ كَانَ عَاقِبَةُ الْمُفْسِدِينَ ١٤

وَاسْتَيْقَنَتْهَا wa-is'tayqanathā · though were convinced with them (signs)

And they rejected them, while their [inner] selves were convinced thereof, out of injustice and haughtiness. So see how was the end of the corrupters. (Surah An-Naml, 27:14)

وَإِذَا قِيلَ إِنَّ وَعْدَ اللَّهِ حَقٌّ وَالسَّاعَةُ لَا رَيْبَ فِيهَا قُلْتُم مَّا نَدْرِي مَا السَّاعَةُ إِن نَّظُنُّ إِلَّا ظَنًّا وَمَا نَحْنُ بِمُسْتَيْقِنِينَ ٣٢

بِمُسْتَيْقِنِينَ bimus'tayqinīna · (are) convinced

And when it was said, 'Indeed, the promise of Allāh is truth and the Hour [is coming] - no doubt about it,' you said, 'We know not what is the Hour. We assume only assumption, and we are not convinced.'" (Surah Al-Jathiyah, 45:32)