अपि: a particle with many uses.

• interrogative
• (prep.) close by or to, within, before; (adv.) further, also, too; even
• at least, however, but
• all (after numerals)
• with an optative verb, expressing hope, fear, or desire; further, moreover, as well as, rather than (usually accompanied by च​, either अपि च​ or चापि).
• they too–who (येऽपि, तेऽपि)
• however, although (यद्यपि)
• even so, nevertheless (तथपि)
• also, may convert an interrogative to an indefinite

Examples:

• अप्यवगच्छसि? – Do you understand?
• अपि सत्यम्? – Is it true?
• अपि कुशलम्? – Are you all right?
• मुहूर्तमपि – only a moment
• कथमपि न – not at all, by no means
• न परं … अपि – not only … but also
• अपीदम् तदीयम्? – Is this his?
• अपीमी अविनीताः? – Are they indisciplined?