Shabbat 104a and Shabbat 104b, the difference between the end-word version of certain letters and how that letter appears at the beginning or middle of a word, a long disquisition on the names and shapes of letters as sending valuable messages of Jewish perspective, and then back to writing– the inks considered permanent enough to violate Shabbat in full, and how connected the two letters need to be to qualify as a Biblical violation (and whether one letter, completing a whole, can count).
