Sy is a given name, nickname/hypocorism (often of Seymour) and surname which may refer to:
Sydney ( ( listen)) is the state capital of New South Wales and the most populous city in Australia and Oceania.
Systemic lupus erythematosus (SLE), also known simply as lupus, is an autoimmune disease in which the body's immune system mistakenly attacks healthy tissue in many parts of the body.
Michael Sylvester Gardenzio Stallone (; born July 6, 1946) is an American actor and filmmaker. He is well known for his Hollywood action roles, including boxer Rocky Balboa in the Rocky series' seven films from 1976 to 2015; soldier John Rambo in the four Rambo films, released between 1982 and 2008; and Barney Ross in the three The Expendables films from 2010 to 2014. Stallone wrote or co-wrote most of the 14 films in all three franchises, and directed many of the films.
Synesthesia is a perceptual phenomenon in which stimulation of one sensory or cognitive pathway leads to automatic, involuntary experiences in a second sensory or cognitive pathway.
A synthesizer (often abbreviated as synth, also spelled synthesiser) is an electronic musical instrument that generates electric signals that are converted to sound through instrument amplifiers and loudspeakers or headphones.