G sus4/C#
The G sus4 chord consists of the G (Perfect unison), C (Perfect fourth) and D (Perfect fifth) notes, with C# as the bass note.

How to play the G sus4/C# chord
- Play C# as the lowest bass note in the left hand
- Find G (Root) on the piano keyboard
- Add C (Perfect fourth) — 5 semitones above G
- Add D (Perfect fifth) — 7 semitones above G
- Press all 4 notes simultaneously to sound the G sus4/C# chord