Cyclones can be classified into
(i) Tropical cyclones
(ii) Temperate cyclones
(iii) Extra Tropical cyclones

Based on the mechanisms of raising the air, there are three types of rainfall.
(i) Convectional rainfall
(ii) Frontal (or) cyclonic rainfall
(iii) Orographic rainfall

(i) Altitude refers to the height above sea level. The temperature decreases at the rate of 6.5^oC per km of height.
(ii) So places at the higher altitude have a lower temperature.

The factors that affect the climate are
(i) Distance from the equator
(ii) Altitude 
(iii) Nearness to the sea
(iv) Nature of the prevailing winds
(v) Mountain barrier
(vi) Cloud cover
(vii) Ocean currents
(viii) Natural vegetation

1. Agriculture was one of the main sources of subsistence.
2. Both wet and dry land farming were practiced.
3. In the riverine and tank-irrigated areas, paddy was cultivated.
4. Millets were cultivated in dry lands.

(i) Coins as a medium of exchange were introduced for the first time in the Sangam Age.
(ii) The coins of the Cheras, the Cholas and the Pandyas, punch-marked coins, and Roman coins form another important source of evidence from the Sangam Age.
(iii) Sometimes coins were protected as a precious wealth.

(i) Parties contest elections. In most democracies, elections are fought mainly among the candidates put up by political parties.
(ii) Parties put forward their policies and programmes before the electorate to consider and choose.
(iii) Parties play a decisive role in making laws for a country. Formally, laws are debated and passed in the legislature.
(iv) Parties form and run the governments.
(v) Those parties that lose in the elections play the role of the Opposition to the party or a group of coalition parties in power, by voicing different views and criticising the government for its failures or wrong policies.
(vi) Parties shape public opinion. They raise and highlight issues of importance.
(vii) Parties function as the useful link between people and the government machinery.

Merits:
(i) As the voters elect their representatives directly, direct elections are considered to be a more democratic method of election.
(ii) It educates people regarding the government activities and helps in choosing the appropriate candidates. Also, it encourages people to play an active role in politics.
(iii) It empowers people and makes the rulers accountable for their actions.
Demerits:
(i) Direct elections are very expensive.
(ii) Illiterate voters sometimes get misguided by false propaganda and sometimes campaigning based on caste, religious and various other sectarian consideration pose serious challenges.
(iii) Since conducting direct elections is a massive exercise, ensuring free and fair elections at every polling station is a major challenge to the Election Commission.
(iv) There are instances of some political candidates influencing the voters through payments in the form of cash, goods or services.
(v) Election campaigns sometimes results in violence, tension, law and order problems and affects the day-to-day life of people.

WIND
(i) The horizontal movement of air along the surface of the earth is called the 'wind'.
(ii) The vertical movement of air is called an 'Air current',
(iii) The winds always blow from a high pressure area to a low pressure area.
PLANETARY WINDS
(i) The winds which constantly blow in the same direction through the year are called the planetary winds.
(ii) These winds are Trade winds, Westerlies and Polar Easterlies.
TRADE WINDS
(i) Trade winds blow from the subtropical high pressure belt to the Equatorial low pressure belt in both the hemisphere.
(ii) They blow in a constant direction throughout the year.
(iii) These winds were very helpful to traders who depended on the winds while sailing in the seas.
WESTERLIES
(i) Westerlies are the permanent wind that blow from the tropical high pressure belt to the sub polar low pressure belt in both the hemispheres.
(ii) The velocity of Westerlies become vigorous.
(iii) It is called Roaring forties at 40^o, Furious fifties at 50^o and Screaming sixties at 60^o latitudes.
POLAR EASTERLIES:
(i) Polar easterlies are cold and dry polar winds that blow from the high pressure belt to the sub polar low pressure belt.

Atmosphere:
The blanket of air that surrounds the Earth is called the atmosphere. The five atmospheric layers are Troposphere, Stratosphere, Mesosphere, Thermosphere and Exosphere.
Troposphere: The lowest layer of the atmosphere is the troposphere. The Greek word 'tropos' means 'turn' or change. The layer extends up to 8 kms at the poles and up to 18 kms at the Equator. The temperature decreases with increasing height. Almost all weather phenomenon take place in this layer. Hence it is called weather making layer. The upper limit of the troposphere is called as tropopause.
Stratosphere: Stratosphere lies above the troposphere. It extends to a height of about 50 km above earth surface. Since this layer is a concentration of ozone molecules, it is also referred as ozonosphere. The temperature increases with increase in height in this layer, Large jet planes normally fly here. The upper limit of the stratosphere is called as stratopause.
Mesosphere: Mesosphere extends between 50km and 80km. The temperature increases with increasing height. Radio waves transmitted from earth are reflected back to earth from this layer: Most of the meteors nearing the earth, get burned here. The uppermost limit of the mesosphere is the mesopause.
Thermosphere: Thermosphere exists above the mesosphere. It extends to about 600 km. The composition of gases in the lower thermosphere is more or less uniform, hence it is called "Homosphere". The upper portion of the thermosphere has uneven composition of gases and hence it is referred as "Heterosphere". Here the temperature increases with increasing height. Ionosphere is a layer of the thermosphere that contains Ions. and free electrons.
Exosphere: The uppermost layer of the atmosphere is called exosphere. This layer is extremely rarefied with gases and gradually merges with the outer space. This zone is characterized by aurora Australis and aurora borealis

1. Sangam age has its roots in the Iron age.
2. In the iron age people were organised into chiefdoms.
3. From such communities of Iron Age emerged the Vendhars of the early historic period.
4. The Velirs of the Sangam Age were chieftains.
5. The Mauryan emperor Ashoka conquered Kalinga and Karnataka.
6. But Ashokan inscriptions are not seen in Tamil Nadu, Therefore we may conclude that the Tamil rulers were independent of Mauryan authority.
7. Among the political powers of the Sangam Age the Cheras, the Cholas and the Pandyas occupied pre eminent position. They were known as Muvendhars.
8. The Muvendhars controlled the major towns and ports of the Sangam period.
9. The Cheras ruled over the region of present day Kerala and Western part of Tamil Nadu.
10. The Cholas ruled over the Kaveri delta and Northern parts of Tamil Nadu.
11. The Pandyas ruled the southern part of Tamil Nadu with Madurai as their capital.
12 Apart from the Vendhars there were Velirs and numerous chieftains.
13. Sangam poems write extensively about the generosity of the people.

Sometimes drizzles are combined with fog and hence reduce visibility.

The economy is classified into three sectors.
1. Primary (or) Agriculture sector,
2. Secondary (or) Industrial sector 
3. Tertiary (or) Service sector.

(i) The term 'pressure group' originated in the USA
(ii) A pressure group is a group of people who are organised actively for promoting and defending their common interest.
(iii) It is so called as it attempts to bring a change in the public policy by exerting pressure on the government.
(iv) They are different from the political parties i.e they neither: contest elections nor try to capture political power.

(i) A political party is an organisation formed by a group of people with a certain ideology and agenda to contest elections and hold power in the government.
(ii) A political party has three components: a leader, active members and the followers.