Alphabet
An alphabet is a standard set of letters written to represent particular sounds in a spoken language. Specifically, letters correspond to phonemes, the categories of sounds 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.
The first letters were invented in Ancient Egypt to serve as an aid in writing Egyptian hieroglyphs; these are referred to as Egyptian uniliteral signs by lexicographers. This system was used until the 5th century AD, and fundamentally differed by adding pronunciation hints to existing hieroglyphs that had previously carried no pronunciation information.