ChaturVarnya

Many words and phrases as used today, have lost their meaning due to misunderstanding, misrepresentation and misinterpretation. It would be worthwhile to think about Cahturvarnya which has undergone mutation.
Varna
First I thought, I would write about 'chatur varnyam', ='the system of classification of humans into 4', but even before venturing onto a deliberation on that word, need to articluate a bit on 'Varna', itself.
Varna means color of course. But varna means many other things too, the most famous of which is 'Akshara' = letter. This latter meaning, is not consequential to the former, meaning, Varna means letter, not because it means color. Letter and color does not have any relation.
Similarly, Varna means the four divisions into Brahmana etc. (Amarkosha 3.3.48 and 2.8.1) and that is not consequential to its meaning, color. So 'color' has nothing to do with 'the classification into 4'
So the concocted explanation some give, saying the classification into 4 given in Gita and other books from India, are based on the color of skin of people, are all fictitious.
ChaturVarnya (CV)
Varna itself means 'the classification into brahmana etc.' Hence 'chatur' in chaturvarnya is actually a repetition. In any case chaturvarnya means the classification into 4 as brahmana, kshatriya, vaishya and shudra. The most famous verse explaining CV is the one from Bhagavad Gita 4:13 which reads as follows:

"cAturvarNyaM mayA sR^iShTaM guNakarmavibhAgashaH
tasya kartAramapi mAM viddhyakartAramavyayaM"

(That is in ITRANS notation, since to my knowledge this editor does not allow devanagari fonts. Readers who are unfamiliar with ITRANS can visit http://en.wikipedia.org/wiki/ITRANS for an understanding of it)

This shloka means, "the classification into four was created by me according to the properties and actions. Although I am the creator of it (this classification) know me as the non-doer, unperishable."
Elsewhere Krishna asks Arjuna to know him as everything in this universe. The Sun, Moon, oceans, good, bad, everything. He is the universe. So the "created by me" in this verse means, it is a creation of the universe, or rather in the universe it is so. That is why he is again saying "know me as the non-doer" because, it just exists so.
The gunas mentioned here are Satva, Raja and Tamah, the serene, active and passive respectively. Individuals need not be of purely one quality. There could be mixture of qualities too.
Depending on these qualities individuals would perform actions too. One who is purely of the Sativik quality and performs actions like, worship of God, teaching, etc. is Brahmana. He has the ultimate knowledge. "Brahmajnaanee thu brahmanaH". Similarly Kshatriya, Vaishya and Shoodra.
It is clear, that the classification is not by birth, but because of one's own qualities and deedes.
I go into explosive laughter when I hear people making comments like "the days of chaturvarnya is over. This is modern times, all are equal" etc.

Dharma

Dharma is another interesting word in Samskrtam. It is derived from the word Dhar, meaning to hold, to support etc. Dharma is therefore used to denote those attributes and activities which makes something. eg. to shine is the Dharma of Sun.
In most cases the Dharma of a THING can be easily derived from the Samskrta name of that THING. eg. Sun is called Bhaskara. Bhas means, shining. Kara means, one who does. So Bhaskara means one who shines. If Bhaskara stops shining then he is not Bhaskara, Sun.Dharma is what makes a Thing.
Pavana means wind. It is derived from Pav, meaning to purify. Pavana is the purifier, like winnowing of corn. For the mordernites, Dharma is the 'core competency'. Focus on your core competency, on your Dharma.
To identify your core competency, observe into yourself. What makes you? What makes you happy? What makes you content?If you don't do what, and not be what, then you wont be you, that is your Dharma.

Padartha

I was just thinking about the word Padartha in Samskrtam. It is a combination of two words, Pada meaning 'word' and Artha meaning 'meaning'. So the word itself means 'word meaning' or 'meaning of word'. Interestingly this word is used to denote 'objects'. So you could say that padartha means 'object'.
For example 'Agni' is Fire. 'Ap' is Water.

To Samskrtam, Agni and Ap are not the names of those objects or things, viz. Fire and Water. Then?
These objects or things are the meaning of the words Agni and Ap.
So a meaning manifests after the word exists. Interesting?