The elementary statements which belong to T {\displaystyle {\mathcal {T}}} are called the elementary theorems of T {\displaystyle {\mathcal {T}}} and said to be true.
Οι στοιχειώδεις δηλώσεις που ανήκουν στη Θ {\displaystyle \Theta } καλούνται στοιχειώδη θεωρήματα της Θ {\displaystyle \Theta } και λέμε ότι είναι αληθή.