Today's daf talks about precision in language. Apparently there was a practice where people would vow their "valuation", meaning a fixed fee based on factors like free/slave status and age (I think!), or their "worth", meaning their market value as workers. A mishna on today's daf highlights the care one must take in wording: if one said "I vow my valuation" and he then died before paying, his heirs must pay. If, on the other hand, he said "I vow my worth" and then died, his heirs do not pay because dead people have no worth. The g'mara explains that this is because his valuation was known at the time he made the oath but his worth wasn't. (20a)