Three consonants carry one idea: to hold back. The same verb stops a car, presses oil from an olive, and locks a suspect in a cell, because all three are forms of stopping a flow. From it Hebrew builds the police term for an arrest, the medical term for being blocked up, and the festival name Atzeret, the day you "hold back" and stay one more night. Every word here 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.
This root lives mainly in the simple pa'al, which already covers a wide spread of meanings from halting traffic to making an arrest. The passive participle עָצוּר and the agent-like עָצִיר below carry the "held back" sense without needing a separate binyan.
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.