Cognates often have a similar meaning, but in some cases the meaning has changed over the centuries in one language or another. An example of such a change is the English word "arena," which usually refers to a sports facility, and the Spanish arena, which usually means "sand." They both come from the Latin harena, which originally meant "sand" and came in time to also refer to an area of a Roman amphitheater that was covered with sand. Spanish retained the meaning of "sand" (although the word can sometimes refer to a sports arena), but English expanded the word's meaning to include facilities something like the Roman amphitheater.
In a popular and less technical sense, the term "cognate" also is used to refer to words in two languages that are similar but have no common origin, such as the Spanish sopa (meaning "soup") and the English "soap."
Also in a popular and not technical sense, the phrase "false cognate" is used to refer to cognates that have different meanings, such as the Spanish molestar (to bother) and the English "molest" (to abuse sexually). A more precise term to use for such word pairs is "false friends."