Road Cycling - What is a century ?

Ok sure 100 miles but how ?
How many breaks are allowed ?
If I do 50 miles and then have 3 hours break and then do the rest 50,is this considered a century ?

A century is generally considered to be 100 miles in a 24 hour period of time preferably done "all at once".

... in other words, many would hesitate to call a 50 mile ride in the first 3 hours of a 24 hour period, then a night's sleep, and then another 50 mile ride the next day, a century.

Some shorten that time period down so it is 100 miles in 12 hours ... but I have done a 15 hour century when it was bitterly cold out and my bicycle kept freezing up on me and I had to keep changing clothes to avoid hypothermia ... and that was a legitimate century because it was done "all at once".

Some organized centuries even have a 7 or 8 hour cut-off.

I think the key is that the ride should be done as "all at once" as possible. Ideally the breaks should be kept fairly short - and you can have as many as you need.

I call a century 100miles in a waking day. That is, no sleeping.

Any 160km ride where the rider, doesn't stop to shower and change (into "normal") clothes, is a century. If a person does 60 km in the morning, comes home and showers, then heads out in the afternoon for another 100km, it is 2 separate rides totalling 160km but not a century. Stopping to eat (a big or small lunch), re-fill bottles etc, is acceptable as not everyone wants to ride 160km non-stop, most people like to enjoy the day as an event.

CHEERS.

Mark