“In math, the backwards E, ∃, means there exists. ∈ means part of a set. A line through that ∉ means excluded from. Everyone ∃, but not everyone ∈.
Simply so, what does it mean when an E is upside down?
The Schwa (Upside Down E) If there's one phonetic symbol Americans are mostly likely to know it's the "schwa" /?/ or "upside down e" for the "uh" sound.
What does a backward 3 mean?
backward E means "there exists" 3. epsilon (looks like c with horizontal line in middle) means "an element of" or "in" of "belongs to" 4. backwards epsilon means "such that" 5. three dots triangle, point up means "therefore" or "thus" 6.
What does an upside down capital A mean?
The upside-down A symbol is the universal quantifier from predicate logic. (Also see the more complete discussion of the first-order predicate calculus.) As others noted, it means that the stated assertions holds "for all instances" of the given variable (here, s).