As I understand it, an abugida is a system where letters represent consonants, and vowels are indicated by diacritics. This includes Brahmi scripts like Tibetan, Devanagari, Thai, etc, and also Ge'ez (Amharic). An abjad is a system where letters represent consonants and vowels are not written - for instance Phoenician. Arabic and Hebrew are not full abjads because some vowels are written.This message has been edited. Last edited by: goofy,
Since many of the vowels aren't written, it's difficult to know how to pronounce the word if you're not familiar with the language. Of course you could say that about any language and any writing system to some extent.