The time signature is written just after the clef (if there are accidentals, they are written between the clef and the time signature)
The top number of the time signature refer to the number of beats in one measure 
The bottom number determine the value of one beat and this number correspond to note values:
| bottom number | value |
| 1 |  |
| 2 |  |
| 4 |  |
| 8 |  |
| 16 |  |
| 32 |  |
| 64 |  |
| 128 |  |
For example 
and 
Time signature examples
4/4 time signature (abbreviated by the letter C)
4/4 time signature means that there are 4 beats per measure and that one beat has for value
Below is an example:
4/4 can be abbreviated by the letter C, this symbol C is called common time
but 4/4 or C are the same:
3/4 time signature
3/4 time signature means that there are 3 beats per measure and that one beat has for value
Below is an example:
2/2 time signature (abbreviated by the symbol 
2/2 time signature means that there are 2 beats per measure and that one beat has for value
Below is an example:
2/2 can be abbreviated by the symbol
but 2/2 or
Changing time signatures
The time signature can change during a melody, here is an example:
Simple and compound meter
Learn the definitions of simple and compound meters. Look at some example of simple meters and compound meters and at the most common time signature.
Odd meter time signatures
All about odd meter time signatures and look at some example of odd meter time signatures. Odd meter is a meter which contains both simple and compound beats.
Difference between 4/4 & 2/2 time signatures
Learn the difference between 4/4 & 2/2 time signatures. Look at an example of difference between 4/4 & 2/2 time signatures with the composer Jean-Philippe Rameau
6/4 time signature example
6/4 time signature example, with explanations and sound samples of famous works by famous composers.
5/4 time signature example
5/4 time signature example, with explanations and sound samples of famous works by famous composers.
4/4 time signature example
4/4 time signature example, with explanations and sound samples of famous works by famous composers.
3/4 time signature example
3/4 time signature example, with explanations and sound samples of famous works by famous composers.
2/4 time signature example
2/4 time signature example, with explanations and sound samples of famous works by famous composers.
4/2 time signature example
Look at an example of a 4/2 time signature, with the musical work Glareanus' Dodecachordon from the french composer Josquin des Prés (1450-1521).
3/2 time signature example
Look at a 3/2 time signature example with the musical work La Sarabande Et Variations from the composer Handel. 3/2 time signature is a triple meter.
2/2 time signature example
2/2 time signature example, with explanations and sound samples of famous works by famous composers.
12/8 time signature example
12/8 time signature example, with explanations and sound samples of famous works by famous composers.
9/8 time signature example
9/8 time signature example, with explanations and sound samples of famous works by famous composers.
6/8 time signature example
6/8 time signature example, with explanations and sound samples of famous works by famous composers.
3/8 time signature example
3/8 time signature example, with explanations and sound samples of famous works by famous composers.
12/16 time signature example
12/16 time signature example with the musical work Sehnsucht de l’œuvre Lieder und Gesänge Op.51 de Robert Schumann. 12/46 is a compound quadruple meter