piano chord
Esus4
E1A4B5
The third replaced by the fourth, which leans on the third it is standing in for.
What is true of it
Esus4 is E, A and B — 1, 4 and 5 counted from E.
These are also the notes of Asus2/E. Which name is right depends on what is underneath and what came before — the notes alone do not decide.