Weak to 1 type
Both have exactly one type weakness
The Weak to 1 type connection is one of the types & combat rules in the daily PokéWired Pokémon puzzle. Two Pokémon are linked by it when this holds: Both have exactly one type weakness.
It's not directional: it works both ways, so it doesn't matter which Pokémon goes on the left and which on the right. It belongs to the Hard rule set, so you'll only run into it in Hard puzzles.
Type connections are the backbone of most chains — they ask about a Pokémon's typing, its weaknesses and resistances, and how one type fares against another in battle.
Examples
Real Pokémon pairs that satisfy the weak to 1 type connection:
Raticate#20Weak to 1 type
Raichu#26Both have 1 weakness — Raticate: Fighting · Raichu: Ground
- Raichu#26Weak to 1 type
Persian#53Both have 1 weakness — Raichu: Ground · Persian: Fighting
- Persian#53Weak to 1 type
Electrode#101Both have 1 weakness — Persian: Fighting · Electrode: Ground
- Electrode#101Weak to 1 type
Kangaskhan#115Both have 1 weakness — Electrode: Ground · Kangaskhan: Fighting