‘se’ (ث), the fifth letter of the Persian alphabet, is, in Persian at least, pronounced exactly like an ‘s’ sound in English, and it is the last of four letters with the same shape as their base, the others being ‘be’ (ب), ‘pe’ (پ) and ‘te’ (ت). The only difference with ‘se’ (ث) is that you draw three dots above the line this time. In this video Keramat shows you how to write the letter in a Persian style along with three example words which show the letter in three different positions:

at the beginning, ثروت—servat—rich
in the middle, مثلث—mosalas—triangle
at the end, اثاث—asās—furniture