When naming a scale one must take notice that every letter must be used as it relates to the piano. The note names come from the first 7 letters of the alphabet (A thru G) and are all used in every scale, depending on the starting note and name, the others are depicted accordingly.
Major Scale Formula is W - W - H - W - W - W- H
Minor Scale Formula is W - H - W - W - H - W - W
(W=Whole Step , H=Half Step)
Example: C Major Scale = C - D - E - F - G - A - B - C
Example: A Major Scale = A - B - C# - D - E - F# - G# - A
Example: F# Major Scale = F# - G# - A# - B - C# - D# - E# - F#
Same Concept applies to Minor Scales as well.
Example C Minor Scale = C - D - Eb - F - G - Ab - Bb - C
Example Eb Minor Scale = Eb - F - Gb - Ab - Bb - Cb - Db - Eb
Example B Minor Scale = B - C# - D - E - F# - G - A - B
Having looked at the rule above an A Major chord is correctly spelled A-C#-E. If a person says A-Db-E, they are talking about the same thing and this is a shortcut used by musicians all of the time but the CORRECT way to dictate an A Major Chord is A-C#-E.
I hope that this clears up how to speak in regards to scales and dictating the correct note names in chords. There are a few note names that seemed funny like E# or Cb but when following the rule they are correctly used so that each scale uses all of the first seven letters of the alphabet.