mater lectionis — a consonant in Hebrew and some other Semitic languages that is used to indicate a vowel (niqqud—the diacritical marks that appear in some Hebrew text above and below the letters—isn’t used consistently and wasn’t an original part of the written language). In some cases the words can be spelled either with or without the matres lectionis.
in Hebrew these are:
א (which has basically lost its original consonant sound)
ה
ו
י
The tendency of Hebrew (et al) to leave out the vowels—the clues to pronunciation—reminds me in a roundabout way of tonal languages. Someone once told me that in some cases people who speak extremely tonal languages can communicate at a distance with just the tone (whistling/drumming), without the actual word. To achieve communication this way, you obviously have to have a fairly good understanding of the language. Likewise, you have to have a decent background in Hebrew to be able to guess at the correct vowels every time (in my not decently backgrounded opinion). It’s pretty neat—like you’re communicating in code. (But I guess all language is really just code.)

April 2nd, 2009 at 1:59 pm
This was always the part that made Hebrew (and Arabic) difficult for me. When you ask a native speaker how they know what the correct sound is you will all get the same answer, “You just know.”