Final answer:
In tennis, the term for a score of zero is 'love', so a score of 0-0 or 15-15 is called 'love'. A tied score of 40-40 is referred to as 'deuce', not 'love'.
Step-by-step explanation:
When the score in a tennis match is tied at either 0-0 or 15-15, the term used is love. The term love in tennis means a score of zero, and its origin is debated, with some suggesting it comes from the French word for egg, "l'oeuf," due to the similarity in the egg's shape and the number 0. However, in tennis, when the score reaches 40-40, which is a tie where each player has won three points, this situation is called deuce, not love.