Nine e of swords are part of the Suite of Swords whose element is air. Air represents thoughts and intellect in the tarot.
Some key words for the nine of swords are anxiety, fear, worry, sleeplessness, and abuse.
The nine of swords appearing in a reading indicates a person who is fraught with worry and anxiety caused by everyday life. This individual may have a lot of negative thoughts about themselves. Sometimes the individual might be making a bigger issue out of things when the issues are really smaller issues. The nine of swords when surrounded by other cards such as the ten of swords, tower or devil tarot cards might also indicate mental illness. Also, the nine of swords could also indicate that a person may have problems sleeping due to nightmares caused by anxiety.
When the nine of swords appears reversed in a reading, the individual is no longer focused on their internal anxiety. However, the individual is actually focusing negativity onto other people which as a result causes fear and anxiety in others.
Want a more comprehensive interpretation of the 78 tarot cards which includes the nine of swords. I highly recommend “The Ultimate Guide to Tarot Card Meanings”, by Brigit Esselmont.