First usage of the symbol ∈ Concerning a book [1] I am reading the symbol $\in$ was first used by Giuseppe Peano and is the first letter $\epsilon$ (epsilon) of the word ἐστί (means "is"). Does anyone know in which work of Peano $\in$ was first used? [1] Ingmar Lehmann, Wolfgang Schulz: "Mengen, Relationen, Funktionen" (3. Auflage, 2007), page 10 Similar question: What is the name of the ∈ symbol and where does it come from?

Concerning < it was first used 1889 in the work _Arithmetices principia nova methodo exposita_ (page X):

> „Signum ϵ significat est. Ita a ϵ b legitur a est quoddam b“

This means something like (my translation which isn't the best!):

> The symbol ϵ means _is_. So a ϵ b has to be read as a _is a_ b

Here is a link to the work: <

The quoted sentence in the original work:

!reference