annāyu

 Annāyu means “living by food” or “desirous of food,” and is used especially as an epithet of the vital air apāna in the Aitareya Upaniṣad.

Core meaning

• The term annāyu (अन्नायु) is glossed as “consisting of, living by food; desirous of food”

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• Multiple dictionaries confirm the same sense: “living by food, desirous of food”

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Grammatical and etymological notes

• Gender: masculine (m.).
• Compound type: a compound of anna (“food”) + āyu (“life,” or in some contexts “obtaining”) according to the lexicographical notes

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• It can function as either:
  • a tatpuruṣa compound (“one who seizes food”), or
  • a bahuvrīhi compound (“one whose life is sustained by food”), depending on context

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Usage in classical texts

• In the Aitareya Upaniṣad, annāyu is used as an epithet of apāna, the downward-moving vital air, because it is the force that “takes” or “seizes” food and thereby sustains life

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• The term is sometimes explained through a pun on āyu (“life”) and the verbal root ī / vī (“to obtain”), which the Upaniṣadic passage plays on

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Related form: annāyus

• A closely related form annāyus (अन्नायुस्) means “living through food”, also used as an epithet of apāna

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• Some commentaries treat annāyu and annāyus as interchangeable in this context.
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Summary

Annāyu is a Sanskrit compound meaning “living by food” or “desirous of food,” most notably used in the Aitareya Upaniṣad to describe the vital air apāna, the bodily function responsible for taking in and processing food.