A sense refers to one of the ways that humans or animals perceive a stimulus. In humans this is normally covers the five senses of hearing, sight, smell, taste or touch. A sixth sense refers to the perception of something that cannot be explained through the application of one of the above five senses.
Sense may also be applied to knowledge, discernment, meaning, value or awareness of something, or a level of practical intelligence. If a word has more than one meaning then these can be described as senses, so for instance "bank" has the senseS of "financial institution" or "side of a river".