Updated: 2021.02.10
רֹאשׁ (m.n.) also denotes the top (as a ladder), the chief (among people), prime (among ministers, e.g., רֹאשׁ הַמֶּמשָׁלָה), or the start (e.g., of a month or year).
Contrast this shōrꞋësh against the unrelated shōrꞋësh, תחל, which more accurately expresses the idea "to begin": הַתְחָלָה.
רִאשׁוֹן, m.n., adj. & ordinal # (e.g., 1st day of the week); pl. רִאשׁוֹנִים.
"The רִאשׁוֹנִים" refers to the "First" European Dark Ages—11th-15th century CE rabbis (which includes RashꞋ"i, Ram•ba"mꞋ and Ram•ba"nꞋ) in contrast to the even more recent, post-15th century CE through today, A•kha•ron•imꞋ rabbis.
רֵאשִׁית, f.n., adj. — Prefix this with the preposition בְּ and you have the name of the first book in Tōr•âhꞋ: בְּרֵאשִׁית !
רֹאשׁ חֹדֶשׁ — 1st of the month
רֹאשׁ בֵּית דִין — בְּכָל מָקוֹם the Chief Justice of the Court: both in the Beit Din hâ-Gâ•dōlꞋ and in every Beit Din ha-Qât•ânꞋ. There is no contradiction of this tradition from the Shi•vᵊimꞋ by the sᵊmikh•âhꞋ of Mōsh•ëhꞋ at Har Sin•aiꞋ until An•tiꞋ•ŏkh•ŏs ŏ Ëp•i•phan•eisꞋ and Yәhō•shuꞋa Bën-Shim•ōnꞋ Jr. Bën-Tzâ•dōq′ ha-Kō•hein′ in BCE 167 when the structure was Hellenized to suit the Roman satrapy Συνέδριον.
רֹאשׁ הַשָּׁנָה — (Babylonian, Christian, or other gentile) New Year
This is only one of a number of assimilations through the millennia that need to be undone.