Letter or alphabet?

WHICH is correct: “big and small letters” or “big and small alphabets”? I tend to pick “letters”. Please give me a lengthy explanation as I would like to show it to my friend. – Azam

An alphabet is defined as “a set of letters or symbols in a fixed order used for writing a language” (Oxford Advanced Learner’s Dictionary, 2005). Thus, the Roman alphabet, which is used for writing English, has 26 letters from A to Z, and the Arabic alphabet used for writing Arabic and Jawi Malay has letters from Alif to Ya. Many Malaysians refer to a letter of the alphabet, such as A or B, as “alphabet A” or “alphabet B”. This is wrong. We should say “letter A” or “letter B”.