A day is (roughly) 24 Hour

It is more accurately 23 Hours, 56 Minutes, and 4 Seconds (And a bit more) for a sidereal day

However a solar day is closer to 24 hours, ranging from 23 hours, 59 minutes and 39 seconds to 24 hours, and 30 seconds

A sidereal day is defined by the rotation of the earth on its axis

However for the sun to be in its exact same position it takes slightly longer as the earth also slightly moves on its orbit around the sun

7 days is a Week

28-31 days make a Month

365(366 on leap years) days make a Year