Iodine is a chemical element with the symbol I and atomic number 53. The name is pronounced  /ˈaɪ.ɵdaɪn/ EYE-o-dyne, /ˈaɪ.ɵdɨn/ EYE-o-dən, or /ˈaɪ.ɵdiːn/ EYE-o-deen in both American and British English. The name is from Greek ἰοειδής ioeidēs, meaning violet or purple, due to the color of elemental iodine vapor.

Iodine and its compounds are primarily used in nutrition, and industrially in the production of acetic acid and certain polymers. Iodine's relatively high atomic number, low toxicity, and ease of attachment to organic compounds have made it a part of many X-ray contrast materials in modern medicine. Iodine has only one stable isotope. A number of iodine radioisotopes are also used in medical applications.

Iodine is found on Earth mainly as the highly water-soluble iodide I^-, which concentrates it in oceans and brine pools. Like the other halogens, free iodine occurs mainly as a diatomic molecule I₂, and then only momentarily after being oxidized from iodide by an oxidant like free oxygen. In the universe and on Earth, iodine's high atomic number makes it a relatively rare element. However, its presence in ocean water has given it a role in biology. It is the heaviest essential element utilized widely by life in biological functions (only tungsten, employed in enzymes by a few species of bacteria, is heavier). Iodine's rarity in many soils, due to initial low abundance as a crust-element, and also leaching of soluble iodide by rainwater, has led to many deficiency problems in land animals and inland human populations. Iodine deficiency affects about two billion people and is the leading preventable cause of intellectual disabilities.

Leonard Norman Cohen, CC GOQ (born 21 September 1934) is a Canadian singer-songwriter, musician, poet, and novelist. His work often explores religion, isolation, sexuality, and interpersonal relationships. Cohen has been inducted into the American Rock and Roll Hall of Fame and both the Canadian Music Hall of Fame and the Canadian Songwriters Hall of Fame. He is also a Companion of the Order of Canada, the nation's highest civilian honour.

While giving the speech at Cohen's induction into the Rock and Roll Hall of Fame on 10 March 2008, Lou Reed described Cohen as belonging to the "highest and most influential echelon of songwriters."

Cohen was born on 21 September 1934 in Westmount, Montreal, Quebec, into a middle-class Jewish family. He attended Roslyn Elementary School. His mother, Marsha Klinitsky, of Lithuanian Jewish ancestry, emigrated from Lithuania while his great-grandfather emigrated from Poland. He grew up in Westmount on the Island of Montreal. His grandfather was Lyon Cohen, founding president of the Canadian Jewish Congress. His father, Nathan Cohen, who owned a substantial Montreal clothing store, died when Cohen was nine years old. On the topic of being a Kohen, Cohen has said that, "I had a very Messianic childhood." He told Richard Goldstein in 1967. "I was told I was a descendant of Aaron, the high priest." Cohen attended Westmount High School, beginning in 1948 where he was involved with the Student Council and studied music and poetry. He became especially interested in the poetry of Federico Garcia Lorca. As a teenager, he learned to play the guitar, and formed a country-folk group called the Buckskin Boys. Although he initially played a regular acoustic guitar as a teenager, he soon switched to playing a classical guitar after meeting a young Spanish flamenco guitar player who taught him "a few chords and some flamenco."