Ten words, three hidden groups of three, and one word that belongs to nobody. Here is how strong players think.
Every Intruder board has exactly ten words. Nine of them form three groups of three that share something: a category, a phrase they complete, a sound, a meaning. The tenth word is the intruder. It usually looks like it belongs to one of the groups, and sometimes to two of them at once. Your job is to submit the three groups; whatever is left standing is the intruder, and the reveal explains why it fooled you.
The puzzle is deliberately built so that at least one group has a fourth candidate. If four words all look like colors, one of them is doing double duty, and the real skill of the game is working out which three the puzzle actually wants.
Do not start with the group that looks biggest. Start with the group where you can name the connection out loud and count exactly three members. If you can say "these three are all knots" and no fourth word could possibly be a knot, submit that first. Every proven group shrinks the board and removes hiding places for the intruder.
When two categories seem to overlap, leave both alone and clear an unrelated group first. Boards are usually designed with one safe group, one medium group, and one trap, and clearing the safe one often makes the trap obvious.
When you submit a wrong trio, Wordcade tells you how close you were. If two of your three words belong together, the message says so, and your selection stays on the board so you can swap a single word instead of starting over. This is the most information-dense moment in the game: you now know two words that are partners and one word that is either the intruder or a member of a different group. Swap one word at a time and watch which substitution succeeds.
A completely wrong trio clears your selection instead. That is also information: none of those three words share a group, which rules out several combinations at once.
The intruder is rarely random. It is chosen because it half-belongs: a fruit that is also a color, a body part that is also a verb, a city that is also a name. When one word keeps feeling like it fits everywhere, that feeling is the puzzle talking to you. The word that fits two groups often fits neither.
Mistakes are counted but not fatal; you can keep trying until you solve the board or give up. A flawless solve, with zero mistakes, is tracked in your stats. If you are truly stuck, a hint costs tokens and is sometimes the right trade on a daily, because winning all three daily games on the first try earns bonus tokens and a Streak Shield, and a shield can save a whole streak later. Giving up shows you the answer but ends the run for that puzzle, so exhaust the near-miss message first.