“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).