A clock is an instrument used for indicating and maintaining the time and passage thereof. In general usage today, however, a "clock" refers to any device for measuring and displaying the time which, unlike a watch, is not worn on the person.

Specific types of clocks
Alarm clock , Flip clock , Astronomical clock , Atomic clock , Balloon clock , Binary clock , Bracket clock ,
Carriage clock , Cartel clock , Chiming clock , Clock network , Clock of the Long Now , Clock tower ,
Congreve clock , Corpus Clock ,Countdown clock , Cuckoo clock ,Data clock , Digital clock ,  Doll's head clock ,  Electric clock ,  Floral clock , Game clock ,  Hourglass , Japanese clock ,  Lantern clock , Lighthouse Clock ,  Grandfather clock ,  Master clock , Mantel clock ,  Musical clock , Pedestal clock , Pendulum clock ,
Projection clock ,  Quartz clock , Radio clock , Railroad chronometer , Reference clock ,

Analog , Atomic, CD & Cassette Player , Digital, Mechanical & Wind-Up,
Travel , Vibrating Alarm Clocks  & Clock Radios  Desk & Shelf ,Calendar & Date  , Roman Numeral Clocks

Floor & Grandfather , Specialty ,  Automatic & Self-Timing , Battery-Operated , Calendar & Date ,
Digital , Large Print & Low Vision ,Moon Phase , Pendulum , Projection , Shower , Sundial ,
Talking ,Weather Monitoring ,Wind-Up ,World Time & Multiple Time Zone , Wall Clocks ,
Analog ,  Digital ,

Style
Casual , Contemporary , International, Traditional ,

Brands
A.S.A.R. , Anelace, BlueMax , Boston Acoustics , Brookstone , Casio, Chaney Instruments , Coby, DAYCLOCK, Digiview , Dream Essentials, Emerson, Enso, Equity ,Get Organized, GPX , Hello Kitty , HoMedics , Honeywell , iHome , jWIN , KNG, La Crosse Technology, Mark Feldstein, Maxi-Aids , Mz Berger , Nanda, Olive Kids , Oregon, Oregon Scientific, Philips, Portmeirion , Rayna Creations, RCA , Reizen , River City Cuckoo Clocks,  Salton, Sangean , Seth Thomas , Sharp, Sharper Image , SKY SCAN , Sony , Sound Design, Inc., Tel-Time, Timex , Tivoli, Verilux , Zelco