tatra

In Sanskrit, 

tatra (तत्र) is an indeclinable adverb (avyaya) that primarily translates to "there" or "in that place."

It is the correlative of yatra ("wherever" or "where") and functions as the locative case of the demonstrative pronoun tat ("that").

1. Primary Meanings

• Location: "There," "in that place," or "thither".
• Contextual/Conditional: "On that occasion," "under those circumstances," "in that case," or "then".
• Referential: "In that matter," "regarding that," or "therein". 

2. Common Usage Patterns

• Tatra tatra (तत्र तत्र): "In various places," "here and there," or "everywhere".
• Yatra tatra (यत्र तत्र): "Wherever," "anywhere," or "at every opportunity".
• Tatrāpi (तत्रापि): "Even there" or "nevertheless". 

3. Samples in Sanskrit Literature

• Bhagavad Gītā (18.78):

  yatra yogeśvaraḥ kṛṣṇo yatra pārtho dhanur-dharaḥ |
  tatra śrīr vijayo bhūtir dhruvā nītir matir mama ||Translation: "Wherever there is Krishna, the master of all mystics, and wherever there is Arjuna, the supreme archer, there (tatra) will also certainly be opulence, victory, extraordinary power, and morality".

• Rāmāyaṇa (7.12.17):

  ...rocayāmāsa tatra vai
  Translation: "...pleased [him] on that occasion [or in that matter]".

• Simple Sentence:

  Alexaha tatra asti.
  Translation: "Alex is there".

   

4. Philosophical Significance

• Vaishnavism: Often used to specify a spiritual location or context, such as referring to Vaikuntha (the abode of Vishnu) or a site where divine pastimes (lila) occur.
• Yoga: Indicates a specific state or condition within a practitioner's internal focus. 

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Note: In modern Hindi, tatra remains an adverb for "there," but should not be confused with tantra (तंत्र), which refers to a system, technique, or body of mystical practices.