Recently, we received a question asking why Logic of English does not use the rule
"Spell with a K for /k/ before E, I, or Y. The letter C is used before A, O, U, or a consonant."
Here was our response:
The Logic of English rules states: “C always softens to /s/ before an E, I or Y; otherwise C says K.” This rule is stated from the perspective of helping students to know which sound the phonogram C will make within a word. This rule is reliable.
The rules you mention are approaching this from a different direction. These rules are trying to summarize how to spell the sound /k/.
If I understand correctly, one rule could be stated, “The sound /k/ is spelled with a K before an E, I or Y.”
While it is true that K is a common spelling of the sound K, CH is used to spell /k/ before an E, I, or Y in over 100 words. (ex. ache, chemistry, orchid, archive, monarchy, hierarchy, pachyderm…) More than 1000 words use CK before and E, I, or Y to spell the sound /k/. (ex. chicken, jacket, locked, backing, icky, stocking, picky, sticky…)
A reliable rule about spelling the sound /k/ would need to say, “The sound /k/ is spelled with a K, CH, or CK before an E, I or Y.” Otherwise, it would generate more than 1000 exceptions.
The second you rule you mention could be stated, “The sound /k/ is spelled with a C before an A, O, or U.”
Interestingly, hundreds of words use a K before an A, O, or U to spell the sound /k/. (ex. Alaska, alkaline, breakable, cockatoo, cookout, koala, kosher, skunk, pickup, haiku, kudos…)
In addition, CK is also used before an A, O, or U as in hundreds of words. (ex. backache, chickadee, jackal, package, beckon, gecko, hickory, checkup…)
And CH is used to spell /k/ before an A, O in words such as mechanic, character, chameleon, anchor, school, chord….
Because there multiple spellings of the sound /k/ and there is no way to know for sure which spelling will be used before and A, E, I, O, or U. The goal of Logic of English is to teach accurate rules that prevent confusion.