One blade cuts two ways. The core of ק־צ־ר is a cut that makes something shorter. Cut the standing grain and you harvest; cut a text and you shorten it. So the same root gives the reaper and the harvest on one side, and shortness, abbreviation, and a summary on the other, even the electrical "short-circuit". Every word below grows from that single act of cutting short. Each 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.
The split between the two binyanim mirrors the split of meaning: the plain pa'al לִקְצֹר keeps the physical, agricultural sense (reap the grain), while the intensive pi'el לְקַצֵּר carries the figurative one (shorten a text, a route, a trip). Same root, two jobs.
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.