Ethiopic

Ethiopic came from the other side of the family. While Phoenician crossed the Mediterranean, the South Arabian scripts crossed the Red Sea into the kingdom of Aksum, carrying the same Proto-Sinaitic inheritance down a separate line. Ethiopic is therefore a sibling of Phoenician, not a descendant of it.

Its great innovation was made independently of the Greek and Indian solutions: rather than add vowel letters, Ethiopic changes the shape of each consonant to show the vowel that follows it. A base consonant has seven "orders," seven small modifications, one for each vowel — which makes it an abugida, not an alphabet or an abjad.

Not a vowel added beside the consonant, but the consonant itself, reshaped.

It began (in South Arabian) as a consonant-only script; the Aksumites added the vocalisation, and around the 4th century CE, under King Ezana, the vowelled system takes hold. Note that the South Arabian branch is often derived directly from Proto-Sinaitic rather than through Phoenician; the site's descent diagram simplifies this — as doctrine here, disputes are recorded, not resolved.

Take a single base consonant — here the l-series — and run it through the seven vowel orders. The modifications are systematic across the script but vary in detail from letter to letter: a stroke, a loop, a foot, a compression of the base. The bare consonant (6th order) is itself just another shape in the set.