There are 24 letters in the greek alphabet, 17 consonants and 7 vowels.
The “ultimate” is the last syllable of a word.
The penultimate is the second to last syllable of a word.
The anti penultimate is the third from last syllable in a word.
The Accent Mark (ο τόνος). Every Greek word with more than one syllable must have a tonos on one of the last three syllables. The tonos shows which syllable to emphasize when saying the word. Emphasis is shown verbally by making that syllable a little louder, drawing it out a little more, or saying it more sharply. (There is a specific rule for certain long words, which have two accent marks, which is not often encountered and will not be covered here). A tonos is also used to distinguish words spelled the same but with different meanings (πως=that and πώς=How?).
The tonos marks the syllable that receives the emphasis. Emphasis is very important. The meaning of words spelled or sounding the same, changes with an emphasis on different syllables.
These Consent Combinations make are all pronounced as one sound not two, and many are pronounced in different ways depending on ones dialect. One example is the sound τσ which is pronounced as /ts/ch/ or a mix of both not found in English. Furthermore, these letter combinations are the only ones that change the letters sound, but they aren't the only combinations. In fact, if any two consonants within the same syllable are next to eachother they are pronounced as one sound. Examples being χτιζω and τεχνη.