(ف) رَبَعَ يَرْبَعُ رَبْعًاrabaʿa yarbaʿu rabʿan: to make four, to be the fourth; also to stay and reside in a place.
اَرْبَعarbaʿ / اَرْبَعَةarbaʿah: the number four (the numeral takes the opposite gender to its counted noun, hence اَرْبَعarbaʿ with a feminine counted noun). ﴿اَرْبَعَةٌ حُرُمٌ﴾ (At-Tawbah 9:36); ﴿اَرْبَعَةَ اَشْهُرٍ وَّعَشْرًا﴾ (Al-Baqarah 2:234)
اَرْبَعُوْنَarbaʿūna: forty. ﴿وَاِذْ وٰعَدْنَا مُوْسٰٓى اَرْبَعِيْنَ لَيْلَةً﴾ (Al-Baqarah 2:51)
رُبَاعrubāʿ: four by four, in fours. ﴿مَثْنٰى وَثُلٰثَ وَرُبٰعَ﴾ (An-Nisāʾ 4:3)
رُبُعrubuʿ: a quarter. ﴿فَلَكُمُ الرُّبُعُ مِمَّا تَرَكْنَ﴾ (An-Nisāʾ 4:12)
رَابِعrābiʿ: fourth. ﴿سَيَقُوْلُوْنَ ثَلٰثَةٌ رَّابِعُهُمْ كَلْبُهُمْ﴾ (Al-Kahf 18:22)
رَبِيْعrabīʿ: the spring season; مَرْبَعmarbaʿ: a place of abode; رَبْعrabʿ pl. رُبُوْعrubūʿ: a settlement, a dwelling-place.
Form II (tafʿīl) رَبَّعَ يُرَبِّعُ تَرْبِيْعًاrabbaʿa yurabbiʿu tarbīʿan: to make square, to make four.