Encodes rank, position, and order relationships.
What It Does
Number.Ordinal neurons activate on ranked or positional quantities — first, second, third, last, penultimate. They fire on both explicit ordinals ('the 5th planet', 'the third-highest peak') and implicit ranking contexts ('the best', 'the top candidate', 'the leading cause'). They encode not just a number but the relationship of that number to a sequence.
How It Behaves
Ordinal neurons concentrate disproportionately in the middle layers, where the model is integrating the positional information with the entity being ranked. This contrasts with Cardinal neurons, which activate earlier. The mid-layer concentration makes sense: ranking requires contextual understanding — 'first' means something different in 'first in line' vs. 'first in the world' — and that disambiguation happens in the middle of the network.
Research Example
In Mistral 7B, Number.Ordinal neurons distinguish between 'the first moon landing' (temporal ordinal) and 'the first moon' (identity/enumeration). This disambiguation is one of the places where hallucinations about historical firsts and rankings originate — Ordinal neurons can activate on the wrong frame of reference.