[2] Byword'd dam Binche made no impact as a racecourse, but has been a very successful broodmare, also producing the multiple Grade I winner Proviso.
A month later he was stepped up in class and won the Listed Prix Pelleas over 2000 metres at Compiègne, with Cirrus des Aigles finishing third.
In September he started odds-on favourite (coupled with his owner's other runner World Heritage) for the Prix du Prince d'Orange at Longchamp Racecourse and finished fourth to Cirrus des Aigles.
On his first appearance as a four-year-old, Byword won the listed Prix Jacques Laffitte on very soft ground at Maisons-Laffitte in April, beating Unnefer "impressively"[6] by two and a half lengths with the odds-on favourite Fuisse in third.
On 16 June, Byword was sent to Britain and started 5/2 favourite for the Group One Prince of Wales's Stakes over ten furlongs at Royal Ascot.
[11] Byword returned to England in August and started 11/4 second favourite for the International Stakes over ten and a half furlongs at York Racecourse.
On his final appearance of the season, Byword started favourite for the Prix Foy at Longchamp in September, but finished fourth behind Duncan, Nakayama Festa and Timos.
After racing just behind the leaders he accelerated into the lead in the last 200 metres and won, easing down, by three-quarters of a length from Vagabond Shoes.
After racing in fifth place, Byword briefly struggled to obtain a clear run in the straight before accelerating in the last 200 metres, catching Cirrus des Aigles in the final strides, and winning by a short neck.
On 5 November he finished eighth behind the 50/1 outsider Court Vision in the Breeders' Cup Mile at Churchill Downs.