A Suspended 4th (Asus4)
1+4+5
Notes in A Suspended 4th
A (root)DE
Inversions
Same notes as A Suspended 4th, with a different chord tone as the lowest note. Useful for smoother movement between chords instead of jumping around the keyboard.
Root position
A in the bass
1st inversion
D in the bass (Asus4/D)
2nd inversion
E in the bass (Asus4/E)
A Suspended 4th consists of A, D and E, played at the same time.
The other suspension raises the missing third up to a perfect fourth, which sits a half step above where the third would normally be. That closeness creates real tension, and it's why a sus4 chord so often falls straight back down into the plain major or minor triad on the same root a beat later.