आत्

{ āt }

A Sanskrit English Dictionary

आत्  n.  ind. ( abl. of 4. अ) afterwards, then (often used in a concluding paragraph antithetically to य॑द्, यदा, य॑दि. and sometimes strengthened by the particles अ॑ह, इ॑द्, ईम्, उ), [RV.]; [AV.]
उ   then, further, also, and, [RV.]; [AV.] It is sometimes used after an interrogative pronoun (like , नु॑, अङ्ग॑) to give emphasis to the pronoun, [RV.]

The Practical Sanskrit-English Dictionary

आत् [āt]   The letter आ. ind. Ved.
Afterwards, then; generally used antithetically to यद्, यदा, यदि and then sometimes strengthened by the particles अह, उ, इद् &c.
Then, further, also, and (अपि च).
Some-times it only strengthens the meaning of another word or gives emphasis to an interrogative pronoun like उ, अङ्ग, नु added to किम् (possibly, at all).