The Ace of Swords is a single upright blade, usually crowned in the older patterns and in Smith's version wreathed as well. The suit descends directly from the Mamluk swords, and unlike coins and cups it has kept its name in every tradition.
Swords is the suit modern readers dread, and it is worth asking why, because the dread is not evenly distributed across tarot history. The Golden Dawn assigned the suit the element air and the faculty of intellect, and the association of thought with suffering is the interpretive move that makes the suit painful. Many of the harshest images in the Rider-Waite-Smith deck are in this suit, and since that deck taught most living readers, the suit's reputation is substantially Smith's doing. In the older pip decks a five of swords is five swords, and carries whatever the reader brings.
For the Ace, the readings are unusually consistent: clarity, a decision made, a truth stated, the moment something becomes definite. The sword's edge cuts both ways in the standard reading, what is clarified cannot be unclarified, and the crown in the older image supplies the note of authority.
The critical readings run to clarity used as a weapon, a truth told for the pleasure of telling it, and the particular cruelty of being right. Waite's reversed meanings run to excessive force and a conception unfulfilled. Readers who do not turn cards find both senses in the upright card and let the spread decide which is operating.
Whichever way it is read, this is a card of the mind rather than the heart, and its arrival in a question about feeling usually means the querent has been thinking about it instead.