A small, tight family around one sense: smell. This is a hollow root, its middle letter is a weak י that hides inside the vowels rather than standing as a hard consonant, so the forms feel short and rounded (re'ach, leha'riach). From the bare noun 'a smell' you build the act of smelling and the quality of being fragrant. Few words, but they show the pattern cleanly: one sense, three roles. 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.
Only one binyan is lexicalized here, the hif'il לְהָרִיחַ, and it is the everyday verb for 'to smell'. Because the root is hollow (middle י), the form contracts: you do not see three full consonants with vowels between them. The pa'al, nif'al, pi'el and passive moulds are not in everyday use for this root.
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.