• تَكْتُمُوا۟
• تَكْتُمُونَ
• تَكْتُمُونَهُۥ
• كَتَمَ
• نَكْتُمُ
• يَكْتُمُ
• يَكْتُمْنَ
• يَكْتُمْهَا
• يَكْتُمُونَ

Appears 20 times in the Quran.

1. 2:33 قَالَ يَٰٓـَٔادَمُ أَنۢبِئْهُم بِأَسْمَآئِهِمْ فَلَمَّآ أَنۢبَأَهُم بِأَسْمَآئِهِمْ قَالَ أَلَمْ أَقُل لَّكُمْ إِنِّىٓ أَعْلَمُ غَيْبَ ٱلسَّمَٰوَٰتِ وَٱلْأَرْضِ وَأَعْلَمُ مَا تُبْدُونَ وَمَا كُنتُمْ تَكْتُمُونَ

   He said: O Adam! inform them of their names. Then when he had informed them of their names, He said: Did I not say to you that I surely know what is ghaib in the heavens and the earth and (that) I know what you manifest and what you hide?
   

2. 2:42 وَلَا تَلْبِسُوا۟ ٱلْحَقَّ بِٱلْبَٰطِلِ وَتَكْتُمُوا۟ ٱلْحَقَّ وَأَنتُمْ تَعْلَمُونَ

   And do not mix up the truth with the falsehood, nor hide the truth while you know (it).
   

3. 2:72 وَإِذْ قَتَلْتُمْ نَفْسًا فَٱدَّٰرَْٰٔتُمْ فِيهَا وَٱللَّهُ مُخْرِجٌ مَّا كُنتُمْ تَكْتُمُونَ

   And when you killed a man, then you disagreed with respect to that, and Allah was to bring forth that which you were going to hide.
   

4. 2:140 أَمْ تَقُولُونَ إِنَّ إِبْرَٰهِۦمَ وَإِسْمَٰعِيلَ وَإِسْحَٰقَ وَيَعْقُوبَ وَٱلْأَسْبَاطَ كَانُوا۟ هُودًا أَوْ نَصَٰرَىٰ قُلْ ءَأَنتُمْ أَعْلَمُ أَمِ ٱللَّهُ وَمَنْ أَظْلَمُ مِمَّن كَتَمَ شَهَٰدَةً عِندَهُۥ مِنَ ٱللَّهِ وَمَا ٱللَّهُ بِغَٰفِلٍ عَمَّا تَعْمَلُونَ

   Nay! do you say that Ibrahim and Ismail and Yaqoub and the tribes were Jews or Christians? Say: Are you better knowing or Allah? And who is more unjust than he who conceals a testimony that he has from Allah? And Allah is not at all heedless of what you do.
   

5. 2:146 ٱلَّذِينَ ءَاتَيْنَٰهُمُ ٱلْكِتَٰبَ يَعْرِفُونَهُۥ كَمَا يَعْرِفُونَ أَبْنَآءَهُمْ وَإِنَّ فَرِيقًا مِّنْهُمْ لَيَكْتُمُونَ ٱلْحَقَّ وَهُمْ يَعْلَمُونَ

   Those whom We have given the Book recognize him as they recognize their sons, and a party of them most surely conceal the truth while they know (it).
   

6. 2:159 إِنَّ ٱلَّذِينَ يَكْتُمُونَ مَآ أَنزَلْنَا مِنَ ٱلْبَيِّنَٰتِ وَٱلْهُدَىٰ مِنۢ بَعْدِ مَا بَيَّنَّٰهُ لِلنَّاسِ فِى ٱلْكِتَٰبِ أُو۟لَٰٓئِكَ يَلْعَنُهُمُ ٱللَّهُ وَيَلْعَنُهُمُ ٱللَّٰعِنُونَ

   Surely those who conceal the clear proofs and the guidance that We revealed after We made it clear in the Book for men, these it is whom Allah shall curse, and those who curse shall curse them (too).
   

7. 2:174 إِنَّ ٱلَّذِينَ يَكْتُمُونَ مَآ أَنزَلَ ٱللَّهُ مِنَ ٱلْكِتَٰبِ وَيَشْتَرُونَ بِهِۦ ثَمَنًا قَلِيلًا أُو۟لَٰٓئِكَ مَا يَأْكُلُونَ فِى بُطُونِهِمْ إِلَّا ٱلنَّارَ وَلَا يُكَلِّمُهُمُ ٱللَّهُ يَوْمَ ٱلْقِيَٰمَةِ وَلَا يُزَكِّيهِمْ وَلَهُمْ عَذَابٌ أَلِيمٌ

   Surely those who conceal any part of the Book that Allah has revealed and take for it a small price, they eat nothing but fire into their bellies, and Allah will not speak to them on the day of resurrection, nor will He purify them, and they shall have a painful chastisement.
   

8. 2:228 وَٱلْمُطَلَّقَٰتُ يَتَرَبَّصْنَ بِأَنفُسِهِنَّ ثَلَٰثَةَ قُرُوٓءٍ وَلَا يَحِلُّ لَهُنَّ أَن يَكْتُمْنَ مَا خَلَقَ ٱللَّهُ فِىٓ أَرْحَامِهِنَّ إِن كُنَّ يُؤْمِنَّ بِٱللَّهِ وَٱلْيَوْمِ ٱلْءَاخِرِ وَبُعُولَتُهُنَّ أَحَقُّ بِرَدِّهِنَّ فِى ذَٰلِكَ إِنْ أَرَادُوٓا۟ إِصْلَٰحًا وَلَهُنَّ مِثْلُ ٱلَّذِى عَلَيْهِنَّ بِٱلْمَعْرُوفِ وَلِلرِّجَالِ عَلَيْهِنَّ دَرَجَةٌ وَٱللَّهُ عَزِيزٌ حَكِيمٌ

   And the divorced women should keep themselves in waiting for three courses; and it is not lawful for them that they should conceal what Allah has created in their wombs, if they believe in Allah and the last day; and their husbands have a better right to take them back in the meanwhile if they wish for reconciliation; and they have rights similar to those against them in a just manner, and the men are a degree above them, and Allah is Mighty, Wise.
   

9. 2:283 وَإِن كُنتُمْ عَلَىٰ سَفَرٍ وَلَمْ تَجِدُوا۟ كَاتِبًا فَرِهَٰنٌ مَّقْبُوضَةٌ فَإِنْ أَمِنَ بَعْضُكُم بَعْضًا فَلْيُؤَدِّ ٱلَّذِى ٱؤْتُمِنَ أَمَٰنَتَهُۥ وَلْيَتَّقِ ٱللَّهَ رَبَّهُۥ وَلَا تَكْتُمُوا۟ ٱلشَّهَٰدَةَ وَمَن يَكْتُمْهَا فَإِنَّهُۥٓ ءَاثِمٌ قَلْبُهُۥ وَٱللَّهُ بِمَا تَعْمَلُونَ عَلِيمٌ

   And if you are upon a journey and you do not find a scribe, then (there may be) a security taken into possession; but if one of you trusts another, then he who is trusted should deliver his trust, and let him be careful (of his duty to) Allah, his Lord; and do not conceal testimony, and whoever conceals it, his heart is surely sinful; and Allah knows what you do.
   

10. 3:71 يَٰٓأَهْلَ ٱلْكِتَٰبِ لِمَ تَلْبِسُونَ ٱلْحَقَّ بِٱلْبَٰطِلِ وَتَكْتُمُونَ ٱلْحَقَّ وَأَنتُمْ تَعْلَمُونَ

    O followers of the Book! Why do you confound the truth with the falsehood and hide the truth while you know?
    

11. 3:167 وَلِيَعْلَمَ ٱلَّذِينَ نَافَقُوا۟ وَقِيلَ لَهُمْ تَعَالَوْا۟ قَٰتِلُوا۟ فِى سَبِيلِ ٱللَّهِ أَوِ ٱدْفَعُوا۟ قَالُوا۟ لَوْ نَعْلَمُ قِتَالًا لَّٱتَّبَعْنَٰكُمْ هُمْ لِلْكُفْرِ يَوْمَئِذٍ أَقْرَبُ مِنْهُمْ لِلْإِيمَٰنِ يَقُولُونَ بِأَفْوَٰهِهِم مَّا لَيْسَ فِى قُلُوبِهِمْ وَٱللَّهُ أَعْلَمُ بِمَا يَكْتُمُونَ

    And that He might know the hypocrites; and it was said to them: Come, fight in Allah's way, or defend yourselves. They said: If we knew fighting, we would certainly have followed you. They were on that day much nearer to unbelief than to belief. They say with their mouths what is not in their hearts, and Allah best knows what they conceal.
    

12. 3:187 وَإِذْ أَخَذَ ٱللَّهُ مِيثَٰقَ ٱلَّذِينَ أُوتُوا۟ ٱلْكِتَٰبَ لَتُبَيِّنُنَّهُۥ لِلنَّاسِ وَلَا تَكْتُمُونَهُۥ فَنَبَذُوهُ وَرَآءَ ظُهُورِهِمْ وَٱشْتَرَوْا۟ بِهِۦ ثَمَنًا قَلِيلًا فَبِئْسَ مَا يَشْتَرُونَ

    And when Allah made a covenant with those who were given the Book: You shall certainly make it known to men and you shall not hide it; but they cast it behind their backs and took a small price for it; so evil is that which they buy.
    

13. 4:37 ٱلَّذِينَ يَبْخَلُونَ وَيَأْمُرُونَ ٱلنَّاسَ بِٱلْبُخْلِ وَيَكْتُمُونَ مَآ ءَاتَىٰهُمُ ٱللَّهُ مِن فَضْلِهِۦ وَأَعْتَدْنَا لِلْكَٰفِرِينَ عَذَابًا مُّهِينًا

    Those who are niggardly and bid people to be niggardly and hide what Allah has given them out of His grace; and We have prepared for the unbelievers a disgraceful chastisement.
    

14. 4:42 يَوْمَئِذٍ يَوَدُّ ٱلَّذِينَ كَفَرُوا۟ وَعَصَوُا۟ ٱلرَّسُولَ لَوْ تُسَوَّىٰ بِهِمُ ٱلْأَرْضُ وَلَا يَكْتُمُونَ ٱللَّهَ حَدِيثًا

    On that day will those who disbelieve and disobey the Messenger desire that the earth were levelled with them, and they shall not hide any word from Allah.
    

15. 5:61 وَإِذَا جَآءُوكُمْ قَالُوٓا۟ ءَامَنَّا وَقَد دَّخَلُوا۟ بِٱلْكُفْرِ وَهُمْ قَدْ خَرَجُوا۟ بِهِۦ وَٱللَّهُ أَعْلَمُ بِمَا كَانُوا۟ يَكْتُمُونَ

    And when they come to you, they say: We believe; and indeed they come in with unbelief and indeed they go forth with it; and Allah knows best what they concealed.
    

16. 5:99 مَّا عَلَى ٱلرَّسُولِ إِلَّا ٱلْبَلَٰغُ وَٱللَّهُ يَعْلَمُ مَا تُبْدُونَ وَمَا تَكْتُمُونَ

    Nothing is (incumbent) on the Messenger but to deliver (the message), and Allah knows what you do openly and what you hide.
    

17. 5:106 يَٰٓأَيُّهَا ٱلَّذِينَ ءَامَنُوا۟ شَهَٰدَةُ بَيْنِكُمْ إِذَا حَضَرَ أَحَدَكُمُ ٱلْمَوْتُ حِينَ ٱلْوَصِيَّةِ ٱثْنَانِ ذَوَا عَدْلٍ مِّنكُمْ أَوْ ءَاخَرَانِ مِنْ غَيْرِكُمْ إِنْ أَنتُمْ ضَرَبْتُمْ فِى ٱلْأَرْضِ فَأَصَٰبَتْكُم مُّصِيبَةُ ٱلْمَوْتِ تَحْبِسُونَهُمَا مِنۢ بَعْدِ ٱلصَّلَوٰةِ فَيُقْسِمَانِ بِٱللَّهِ إِنِ ٱرْتَبْتُمْ لَا نَشْتَرِى بِهِۦ ثَمَنًا وَلَوْ كَانَ ذَا قُرْبَىٰ وَلَا نَكْتُمُ شَهَٰدَةَ ٱللَّهِ إِنَّآ إِذًا لَّمِنَ ٱلْءَاثِمِينَ

    O you who believe! call to witness between you when death draws nigh to one of you, at the time of making the will, two just persons from among you, or two others from among others than you, if you are travelling in the land and the calamity of death befalls you; the two (witnesses) you should detain after the prayer; then if you doubt (them), they shall both swear by Allah, (saying): We will not take for it a price, though there be a relative, and we will not hide the testimony of Allah for then certainly we should be among the sinners.
    

18. 21:110 إِنَّهُۥ يَعْلَمُ ٱلْجَهْرَ مِنَ ٱلْقَوْلِ وَيَعْلَمُ مَا تَكْتُمُونَ

    Surely He knows what is spoken openly and He knows what you hide;
    

19. 24:29 لَّيْسَ عَلَيْكُمْ جُنَاحٌ أَن تَدْخُلُوا۟ بُيُوتًا غَيْرَ مَسْكُونَةٍ فِيهَا مَتَٰعٌ لَّكُمْ وَٱللَّهُ يَعْلَمُ مَا تُبْدُونَ وَمَا تَكْتُمُونَ

    It is no sin in you that you enter uninhabited houses wherein you have your necessaries; and Allah knows what you do openly and what you hide.
    

20. 40:28 وَقَالَ رَجُلٌ مُّؤْمِنٌ مِّنْ ءَالِ فِرْعَوْنَ يَكْتُمُ إِيمَٰنَهُۥٓ أَتَقْتُلُونَ رَجُلًا أَن يَقُولَ رَبِّىَ ٱللَّهُ وَقَدْ جَآءَكُم بِٱلْبَيِّنَٰتِ مِن رَّبِّكُمْ وَإِن يَكُ كَٰذِبًا فَعَلَيْهِ كَذِبُهُۥ وَإِن يَكُ صَادِقًا يُصِبْكُم بَعْضُ ٱلَّذِى يَعِدُكُمْ إِنَّ ٱللَّهَ لَا يَهْدِى مَنْ هُوَ مُسْرِفٌ كَذَّابٌ

    And a believing man of Firon's people who hid his faith said: What! will you slay a man because he says: My Lord is Allah, and indeed he has brought to you clear arguments from your Lord? And if he be a liar, on him will be his lie, and if he be truthful, there will befall you some of that which he threatens you (with); surely Allah does not guide him who is extravagant, a liar: