Gamma is used when the 1 club opener raises a positive bid on 1 club (1H/1S/2C/2D) on level. Opener makes a single raise of that suit to ask about the quality of it.
Ex: 1C-2D-3D or 1C-1H-2H
Answer on Gamma:
1. step: 0 top honors.
2. step: 1 top honor. 5 cards.
3. step: 2 top honors. 5 cards.
4. step: 1 top honor. At least 6 cards.
5. step: 2 top honors. At least 6 cards.
6. step: All three top honors.

If partner shows 1 honor you can bid the suit again:
1. step: Queen
2. step: King
3. step: Ace

NB! Gamma is most used after a Beta bid.
1C - 1S
1NT- 2H (Answer on Beta)
2S (Gamma)