[nai](aux-adj) (1) not (verb-negating suffix; may indicate question or invitation with rising intonation); (suf, adj-i) (2) (See 忙しない) emphatic suffix (used after the root of an adjective); (P)#27[Add to Longdo]
[nu](aux-v, suf) (1) (See ない・1, ません, ん・2) (after the -nai stem of a verb) not (verb-negating suffix); (2) (arch) indicates completion#1639[Add to Longdo]