Based on the English alphabetical order, three of the following four…

CONCEPT: In an alphabet letter-cluster classification item, three of the four clusters usually share a fixed numeric relationship between their letters’ absolute alphabet positions (A = 1, B = 2, ..., Z = 26) — most often a constant step from one letter to the next, wrapping from Z back to A when the count runs past 26. The cluster whose letters do not carry that same constant step is the one that does not belong to the group.

APPLICATION: Convert every letter to its alphabet position and check the step between consecutive letters in each cluster:

1. NTZ: N = 14, T = 20, Z = 26. Step N→T = 20 − 14 = 6; step T→Z = 26 − 20 = 6 — both steps equal 6.

2. UAG: U = 21, A = 1, G = 7. Step U→A = (1 + 26) − 21 = 6, counting past Z; step A→G = 7 − 1 = 6 — both steps equal 6.

3. GMS: G = 7, M = 13, S = 19. Step G→M = 13 − 7 = 6; step M→S = 19 − 13 = 6 — both steps equal 6.

4. SYI: S = 19, Y = 25, I = 9. Step S→Y = 25 − 19 = 6; step Y→I = (9 + 26) − 25 = 10, counting past Z — this step is 10, not 6.

CROSS-CHECK: Verify SYI independently by working from the other direction — adding 6 to Y (25) gives 31, which wraps to position 5 (E), not I (9); and subtracting a wrapped step of 6 from I (treated as 9 + 26 = 35) gives 29, which wraps to position 3 (C), not Y (25). No constant step of 6 connects Y and I in either direction, while NTZ, UAG, and GMS each independently confirm a consistent step of 6 between every consecutive pair, including the wrap-around cases.

RESULT: Three of the four clusters — NTZ, UAG, and GMS — share a constant +6 alphabetical step between consecutive letters (wrapping past Z where needed). SYI breaks that step, so SYI is the letter-cluster that does not belong to the group.