How many categories of forbidden labor (avot melachot) exist on Shabbat?
39 avot melachot — derived from the 39 types of creative work done to build the Mishkan (Tabernacle). Each has derivative sub-categories (toldot).
Question 2
Where are the 39 melachot derived from?
The 39 melachot correspond to the 39 types of creative work performed in constructing the Mishkan — God's dwelling place in the desert.
Question 3
Is a toldah (derivative labor) less severe than its parent av (category)?
A toldah carries the same Torah-level prohibition as the av. The distinction between av and toldah affects which sin-offerings are brought, not the severity of the prohibition.
Question 4
What is the standard minimum measure for food-related Shabbat violations?
A dried fig's bulk (k'grogeret) is the standard shiur for most food-related labors on Shabbat. Below this amount, there's no Torah liability (but it remains rabbinically forbidden).
Question 5
A person unknowingly performs multiple forbidden labors on Shabbat. What happens?
Each category of labor violated requires its own sin-offering. If someone unknowingly plowed, sowed, and reaped — three separate offerings.