Joined letters

Within a word Arabic letters join each other, so a letter looks slightly different depending on its position: at the start, in the middle, at the end, or alone.

The six letters that never join the next one

ا د ذ ر ز و

They join the letter before them but not the one after. In دَارٌ (daarun) all three letters stand apart.

Practice — read these

بَتَ — تَبَ — بَلَ — كَتَبَ — جَلَسَ — ذَهَبَ — خَلَقَ — عَلِمَ