Under all of these sits the number four. Four sides make a square; one part of four is a quarter; the fourth in a series is revi'i; a city quarter is a rova. Even the verb 'to square' (multiply by itself toward a four-sided figure) and the animal-breeding 'to mate' (pairing, doubling) lean on this idea of four-ness and pairing. Do not confuse ר־ב־ע (four) with ר־ב־ה (many) from the previous page: ayin versus weak ה. Every word is verified against pealim, niqqud included.
The same root runs through the verb system. Each binyan is a voice: it bends the one idea into active, passive, causative or reciprocal. Tap to hear.
Two binyanim, both built off the same numeric core: the pi'el shapes a four-sided figure (to square), and the hif'il causes a pairing (to mate animals). The pa'al, nif'al and passive moulds are not lexicalized for this root; the everyday forms you meet are the nouns and adjectives below.
Same root letters, different noun moulds (mishkalim). The mould tells you the function: who does it, the act of doing it, or the thing produced.
Strip the prefixes, suffixes and vowels. Three consonants remain, and the meaning lives there.