Alphabet
An alphabet is a writing system that uses a standard set of symbols called graphemes – more commonly known as letters – to more or less represent particular sounds in a spoken language. Specifically, these graphemes largely correspond to phonemes, which are the smallest sound segments that can distinguish one word from another in a given language. Not all writing systems represent language in this way: a syllabary assigns symbols to spoken syllables, while logographies assign symbols to words, morphemes, or other semantic units.
Read on Wikipedia