Choose the appropriate word which can be substituted for the given sentence: 'One who does not believe in the existence of God'.

Choose the appropriate word which can be substituted for the given sentence: $A$ government by the nobles.

Choose the appropriate word which can be substituted for the given sentence: $A$ person who tries to deceive people by claiming to be able to do wonderful things.

Choose the appropriate word which can be substituted for the given sentence: 'Something that relates to everyone in the world'.

Choose the appropriate word which can be substituted for the given sentence: Study of birds.

Choose the appropriate word which can be substituted for the given sentence: 'One who sacrifices his life for a cause'.