1. A mark; such as, (") which is used to indicate the word above it should be repeated: "When filling out the application form for a job, Alfred used dittos to show that the information which was wanted was the same as that which he had just written in the space above it."
2. Used instead of repeating something that has just been said to indicate that the same thing applies to you; such as, "I was bored with that speech." "Ditto for me, too."
3. A duplicate; a copy: "It was amazing! The son was a complete ditto of his father!"
4. Etymology: from Tuscan dialect ditto, "(in) the said (month or year)"; from Italian detto, past participle of dire, "to say"; from Latin dicere, "a saying, an expression, a word"; from dic-, stem of dicere, "to speak, to tell, to say".

Originally, "ditto" was used in Italian to avoid the repetition of month names in a series of dates; generalized meaning of "same as above" was first recorded in English in 1678.