That depends on what you're relating the spin to. If the Earth did not spin relative to space itself, there would be a diurnal cycle. However, each 'day' would last half a year, with the other half occupied by one night. If the Earth did rotate, but did not rotate relative to the Sun, we would be in much the same situation the Moon is in with us - one face always showing to the Sun, the other always hidden. In this scenario, we would have no diurnal cycle.
Earth's rotationEarth's rotation
each day at noon
One tidal cycle per day; for more details see http://en.wikipedia.org/wiki/Tide#Timing.
they are what you call when there are two tide cycles in one day--when there is only one tide cycle in one day that is called diurnal--diurnal tides occur in the Gulf of Mexico.
The Earth won't, actually can't stop spinning in a human timescale.
Diurnal cycle
Diurnal cycle
During the diurnal cycle the Earth has completed one rotation which takes 24 hours. The diurnal cycle refers to any pattern that repeats itself every 24 hour.
Earth's rotationEarth's rotation
Seasonal cycle
The spinning of the Earth affects the Earth's water by creating currents and winds. The spinning of the earth is necessary to complete the water cycle and establish weather patterns.
Earth's rotationEarth's rotation
Very little as it is spinning at a constant speed. However, the moon does affect the Earth's seas, greatly.
== 1. (biology) belonging to or active during the day; "diurnal animals are active during the day"; "diurnal flowers are open during the day and closed at night". 2. Having a daily cycle or occurring every day; "diurnal rhythms"; "diurnal rotation of the heavens"; "the diurnal slumber of bats".
Day is an arbitrary word for the period of light in the Earth's diurnal cycle. When the sun is "up" there is more light, so it is "day"
An antonym to diurnal is nocturnal when diurnal is defined; of or belonging to or active during the day; "diurnal animals are active during the day"; "diurnal flowers are open during the day and closed at night" Another antonym to diurnal is aperiodic (vs. periodic) when diurnal is defined; having a daily cycle or occurring every day; "diurnal rotation of the heavens" ~gpack
Because earth is so big that we can't feel it spinning unless you are at the middle of the core.