piano chord
Asus4
A1D4E5
The third replaced by the fourth, which leans on the third it is standing in for.
What is true of it
Asus4 is A, D and E — 1, 4 and 5 counted from A.
These are also the notes of Dsus2/A. Which name is right depends on what is underneath and what came before — the notes alone do not decide.