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    Why Is <broad> Spelled with the <oa> Digraph?

    Why Is Spelled with the Digraph?

    Yesterday I posted on my social media about the spelling of the word <broad>. I just introduced the <oa> grapheme to my 5-year-old. The digraph <oa> typically spells the phone [oʊ] as in <oak>, <boat>, <soap>, <road>, and <hoax>. So why does the <broad> spell [bɹɔd] (or [bɹɑd] in Englishes with the cot-caught merger)?

    The primary function of English spelling is to represent meaning. Structured Word Inquiry (SWI) is a means by which to study spelling. One can use SWI to investigate spelling by asking four questions:

    1. What does a word mean?
    2. How is the word built?
    3. What are morphological and etymological relatives of the word?
    4. What are the sounds that matter?

    The questions are to be investigated in order.

    Question 1: What does <broad> mean? <broad> means “wide.”

    Question 2: How is <broad> built? <broad> consists of one free base: <broad>. <broad> is a lexical word.

    Question 3: What are the relatives of <broad>? Modern <broad> comes from Old English <brad> meaning “wide, not narrow.” Some related words include <abroad>, <broadly>, <broaden>, and <broadness>. <broad> is also related to <breadth>, which means “wide range or extent, width.”

    Question 4: What sounds matter? <broad> spells [bɹɔd] or [bɹɑd]. The graphemes are <b.r.oa.d>.

    But why does the <oa> spell [ɔ] or [ɑ] in <broad>. The graphemes <o> and <e> bear an etymological relationship as in <get> and <got> and <feet> and <foot>. The digraph <oa> also bears a relationship with <ea> as in <great> meaning “big” and <groat> meaning “a large coin.” The word <bred> is spelled with the grapheme <e> because of a relationship with the <ee> digraph in <breed>. In accordance with the homophone principle, English prefers to have different spellings for words that sound alike but have different meanings. The <e> in <bred> thus distinguishes the word from the <bread> in <breadth>. <broad> is spelled with an <oa> to preserve the relationship with word <breadth>.

    The digraph <oa> usually spells the phone [oʊ] as in <oat>, <loaf>, <soak>, <toad>, and <float>. In the word <broad>, however, the <oa> spells [ɔ] or [ɑ] depending on your English. Just as <o> and <oo> are related to <e> and <ee>, <oa> is related to <ea>. The <oa> in <broad> thus preserves the relationship with the <ea> in <breadth>. Understanding the spelling of <broad> is possible only by considering the history and relatives of the word in addition to the sounds.

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