This root holds two strands that the bare letters ש-ע-ר disguise. With shin (שׁ) it is the gate and, by extension, anything that stands at a threshold and gets measured: an exchange rate, a lesson portioned out, a value estimated. With sin (שׂ) the very same skeleton means hair, and from it barley (the bearded grain). The verb לְשַׁעֵר "to estimate" comes from setting a value at the gate; לְהַשְׂעִיר "to grow hair" comes from the other strand. One spelling, two worlds. 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.
The two verbs belong to the two strands and are spelled apart by the sibilant: לְשַׁעֵר uses shin (the gate/measure strand, hence "estimate"), לְהַשְׂעִיר uses sin (the hair strand). Same consonant skeleton on the page, different sound and different meaning, the classic shin/sin trap.
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.