A hybrid bicycle is a bicycle designed for general-purpose utility and commuting on a wide variety of surfaces, including paved and unpaved roads, paths and trails. It combines features from the road bike and the mountain bike, and includes variants such as the city bike, cross bike and commuter.
In general, hybrids use the mountain bike's triple crank, its handlebars, giving a more upright posture than road bicycles, and its brakes such as linear pull or disc. From the road bicycle they often take the 700c (larger) wheel diameter for higher speeds, but use a wider rim and tire for increased strength.
A trekking bike is a hybrid with all the accessories necessary for bicycle touring - mudguards, pannier rack, lights etc
Similar to the commuter bike, the city bike is optimized for the rough-and-tumble of urban commuting. The city bike differs from the familiar European city bike in its mountain bike heritage, gearing, and strong yet lightweight frame construction. It usually features mountain bike-sized (26-inch) wheels, a more upright seating position, and fairly wide 1.5 - 1.95-inch (38 - 50 mm) heavy belted tires designed to shrug off road hazards commonly found in the city, such as broken glass.Using a sturdy welded chromoly or aluminum frame derived from the mountain bike, the city bike is more capable at handling urban hazards such as deep potholes, drainage grates, and jumps off city curbs. City bikes are designed to have reasonably quick, yet solid and predictable handling, and are normally fitted with full fenders for use in all weather conditions. A few city bikes may have enclosed chainguards, while others may be equipped with suspension forks, similar to mountain bikes. City bikes may also come with front and rear lighting systems for use at night or in bad weather.