The definite article

One of the things many should have noticed before embarking on learning the Arabic language, is the frequent use of prefixes like "Al" or "El". "Al" and "El" are the same two letters "a" and "l" put together, which indicate the definite article for a noun. But what is considered definite and what is not, is often different from many Western languages. Briefly one could make this as a rule: If it is not particularly important to stress the indefinite form, the definite article should be used. But this is only a valid rule at your present stage in learning Arabic.
When a noun is indefinite, no prefixes or suffixes are added, you simply use the core form of the noun.
Just to complicate things a bit here: In Arabic there are a group of "sun letters", letters which standing first in a noun, eat the "l" of the definite article. These are the following letters:

The result is that you never write it in English transcription nor pronounce the l: "al-t.....", "al-th....", "al-d....", "al-dh....", "al-r....", "al-z....", "al-s....", "al-sh...." and so on.
What you do write and pronounceis : "at-t....", "ath-th....", "ad-d....", "adh-dh....", "ar-r....", "az-z....", "as-s....", "ash-sha....." and so on. However, when you write it in Arabic, the letter "l" is written, but that is for later lessons.
For the remainder of the letters, you leave the "l" of the definite article intact.