What is preposition????

Prepositions of time 1
A.We use at with an exact point of time, times of the day and festival
Use Examples
Exact point of time : I get up at six in the moring.
Festivals : Children like to see christmas Father at Christmas.
Meals and mealtimes: I shall see you at lunch-time.
Times of the day: I used to study at night.
B.We use on with days and dates. parts of particular day or special
days.
Use Examples
Days and dates: Ther will be a test on Monday.
Parts of a particlar day: We webt shopping on Monday evening.
Special days: We go to the church on Easter Sunday.
C.We use in for longer periods of time and parts of day.
Use Examples
Longer periods of time: It is very hot in August.
Parts of the dat: What are you doing in the afternoon?

Prepositions of time 2
A. We also say in the past and in the future.
B. We use in before a period of time t talk about when something will
happenin the future.
C. We use from...to ...or from...till( untill )...to say that something
began at one time and finished at a certain time.
D. We can use between...and...instead of form...to...
E. Do NOT use a preposition before last, naxt, this, every,
tomorrow or yesterday.

2009-01-18 12:31:06 補充：
A preposition is a word used to show the relationship of a noun to something else, usually a location in space or time. A preposition is one type of a larger grammatical category referred to as adpositions.

In grammar, a preposition is a part of speech that introduces a prepositional phrase. For example, in the sentence "The cat sleeps on the sofa", the word "on" is a preposition, introducing the prepositional phrase "on the sofa". In English, the most used prepositions are "of", "to", "in", "for", and "on". Simply put, a preposition indicates a relation between things mentioned in a sentence.
(extract from Wikipedia)

http://en.wikipedia.org/wiki/Preposition
I hope I can help you.

The general meaning of preposition is [placed before]
Generally used prepositions are : in, on, at, to ,from, up , down,
towards, away, off, about, around, round, under and above etc.
eg. in the box, on the table, under the tree, near the window,
prepositions are always placed before nouns.
Sometimes prepositions can be placed after nouns.
eg. a man of great power, a book about philosophy, a flower with
different colors, a cup of coffee, a bundle of bananas etc.
Prepositions can form prepositional phrases to modify nouns or verbs.
eg. The children are playing in the garden. [in the garden] is an
adverbial prepositonal phrase of place to modify the verb [are
playing].
The monkey is looking at a girl with long hair.
[with long hair] is an adjectival prepositonal phrase to modify the
noun [girl].

In some languages, a word placed before a substantive and indicating the relation of that substantive to a verb, an adjective, or another substantive, as Englishat, by, in, to, from, and with.

a word or group of words e.g. in,from, to out of, on behalf of) often placed before a oun or pronoun to indicate place, direction, source, method, etc.