Question: There are many versions of Vedanta available and most of them have drastic differences and contradictions. 

**So is Vedanta is a loosely coined term or does it have a concrete definition?** 

**What is its relation to the philosophy?** 

If veda-anta is something **beyond/other** than the Vedas then it cannot be called as **vedanta** at all. 

**Further, there are no divisions such ad Veda-aadi, veda-madhya then how come we have something like veda-anta?**

If its a part of the Vedas then these philosophies also form the part of the so called KarmakAnda.

Answer: 
You can get unabridged Devi Bhagavata Purana and Markandeya Purana in Sanskrit and English with verse by verse translation from [IndianScriptures site](http://www.hinduscriptures.in/). Here are links for them.

* [Devibhagavata Purana](http://www.hinduscriptures.in/scriptures/upa-purana/srimad-devibhagavatam)
* [Markandeya Purana](http://www.hinduscriptures.in/scriptures/puranas-18-puranas-mahapurana/markandeya-purana)

Each Chapter is uploaded as separate pdf file on that site.

You can also read **Lalita Mahatmya** of Brahmanda Purana which describes glory of Mother Lalita. You can get Brahmanda Purana in English from [this answer](https://hinduism.stackexchange.com/a/9095/3500).

You can also visit below question for more resources.

[What are some online sources to get unabridged Hindu Scriptures or to learn Hinduism?](https://hinduism.stackexchange.com/q/15424/3500)
Gita Press Gorakhpur is an online site that offers books on Indian Religion and Mythology at unbelievable prices. You should check that out.