The Phoenicians did not invent their alphabet, they inherited an older alphabet.

Nevertheless they had a very important role in spreading the alphabetic writing system to many other populations, which was a consequence of their travels and commercial relations with everybody around the Mediterranean and even farther away.

Because of this, the ancestry of the majority of the alphabetic systems, even of some far away in South Asia can be traced back to the Phoenician alphabet.

Because of the importance of the commerce with Phoenicians and because of the many Phoenician colonies, the Phoenician language has also been spoken by many non-Phoenicians. This had as a consequence a simplification of the pronunciation of the Phoenician language, because for most foreigners it was difficult to pronounce some of the sounds specific to the Semitic languages.

The result of this simplification in pronunciation was that the number of letters of the Phoenician alphabet has been reduced to 22 letters from the 27 letters of the older North-Semitic alphabet inherited by the Phoenicians, because some of the sounds that were written with different letters in the older alphabet have evolved towards an identical pronunciation, so eventually the redundant letters from each pair with the same pronunciation have been dropped.

22 letters is a too small number for most languages, which has forced those who have adapted the Phoenician alphabet to other languages to add supplemental letters, like in the Greek alphabet, then in the Latin alphabet.

The small number of letters has created problems also for the writing of other Semitic languages, like Aramaic, Hebrew and Arabic, which did not have the simplified pronunciation of Phoenician. The older North-Semitic alphabet from which the Phoenician alphabet had been derived would have been perfect for such Semitic languages, but by the time when writing has spread from the Phoenicians to their Semitic neighbors the older Semitic alphabet had been forgotten, exactly in the same way (and probably for the same reasons) as the Mycenaean writing had been forgotten in Greece (i.e. toward the end of the 2nd millennium BC there have been a few centuries of "Dark Ages" when much prior knowledge had been lost, after the destruction of many cities).

Because the older Semitic alphabet had been forgotten, the Hebrew alphabet has 22 letters derived from the Phoenician alphabet through the Aramaic alphabet, despite the fact that this number was not enough to write all the consonants of ancient Hebrew. One Hebrew letter has now 2 variants distinguished with diacritic marks, i.e. "shin" and "sin", because originally it was used to write 2 different sounds, one of which no longer existed in Phoenician (modern Hebrew has lost that sound, so now "sin" and "samekh" are pronounced in the same way).

Writing has been invented independently in many places around the world, but in almost all writing systems the written symbols have been used to denote either syllables or words.

The Egyptian writing system and the alphabetic writing systems, all of which have been derived from the Egyptian writing system, are the exception.

A subset of the symbols of the Egyptian writing system was used to denote single consonants, while the remainder were used to denote multiple consonants, regardless of which vowels were pronounced together with the consonants.

The ancient Semitic alphabet has simplified the Egyptian writing system by retaining only the symbols that denote a single consonant. The ancient Semitic alphabet has retained thus the principle of writing only the consonants, and it has also inherited from the Egyptians the direction of writing from right to left, which has been preserved in the Hebrew and Arabic writing systems. Besides changing the meaning of some Phoenician letters from consonants to vowels, developing thus the first alphabetic writing system in the restricted meaning of the term "alphabet", i.e. with an approximately one-to-one mapping between all phonemes and letters, not only between consonants and letters, the Greeks have reversed the writing direction and this has been inherited in the other European writing systems.