In 【Only Sense Online】, the players are all equipped with abilities called 'Senses'.
A Sense is an equippable talent that exists separately from the normal equipment like weapons. While equipped, a Sense can give you a permanently active ability, allow you to use certain skills, have an effect on various actions, or provide corrections and multipliers during the game.
Up to 10 Senses can be equipped at once. An acquired Sense does not have to be equipped, and can be kept as backup. The Senses can be freely re-equipped.
For every 10 levels gained in sense, the player gains one free SP and gain further Senses.
See: Sense List for a list of known senses (and a few speculative).