The phrase "alternate letter" is correct and usable in written English.
It can be used when referring to a letter that is used in place of another letter, often in a pattern or sequence.
Example: "To create a unique code, we will use an alternate letter for each vowel in the message."
Alternatives: "substitute letter" or "replacement letter".
"Watch your mailbox so you can say 'Yes' to continue Chase debit card overdraft coverage," read one note, a toned-down version of an alternate letter warning consumers that their debit card might not cover unexpected emergencies, like a highway tow. 1 2 Next Page ».
However, in practice we must discriminate these two cases using discrete counts of the number of reads that report an alternate letter.
Nucleotide changes from the reference sequence were called where at least six separate reads called the alternate letter, and the sum of the Illumina quality scores of the alternate letter from all reads containing that letter were 5× the sum of the Illumina quality score of the reference letter in all of the reads that contained that letter.
(say on a + alternate letters; Saga, Japanese city).
Sure, must on leaving each other (anag. of alternate letters, & lit.; must4).
D. Appleton: Goodbye, son – for ever going abroad, defying the odds (s ay + alternate letters).
S. Randall: Settlement's bones originally Aurignacian indicating regular sacrifices (b + alternate letters).
M. L. Perkins: Oval, perhaps, where a rising ball may break up odd bits of the pitch which are out of true (pill (rev). in anag. of alternate letters).
Help! – bring it back in! (straight … beam; aid (rev). in anag).. R. J. Heald: Frightfully odd things in an Alice adventure start in a dream (dart in a stream; anag. of alternate letters).
Ring AA for breakdown truck (b anger) + anag).. M. Lloyd-Jones: Snip short fringe – locks are glam if regularly cut (are glam if less alternate letters in ban(g)).
(t for U in cube + R, & lit).. P. McKenna: It is consumed by those leading CAMRA but ends in possible hangover ('t in first letters and last letters, & lit).. G. McStravick: One finds this time evoked by Dowson's poem (recitable, getting odd bits wrong) (anag. of alternate letters).
