二【に】
two, 2
二人【ふたり】
two persons, two people, pair, couple
二つ【ふたつ】
two
二階【にかい】
second floor, upstairs
二重【にじゅう】
double, two-fold, two layers, duplex, diplo-, dipl-, double-edged eyelid, double eyelid, creased eyelid
二次【にじ】
second, secondary, quadratic (function, equation, etc.), second-order
二階建て【にかいだて】
two-storied building
二世【にせい】
nisei, second-generation Japanese (or Korean, etc.), person of Japanese parentage with non-Japanese citizenship, the second (e.g. Edward II), son
一石二鳥【いっせきにちょう】
killing two birds with one stone
二者択一【にしゃたくいつ】
choosing between two things, two choices
二流【にりゅう】
second-rate, inferior
二枚舌【にまいじた】
double-dealing, duplicity, equivocation, double-tongued
二重奏【にじゅうそう】
instrumental duet, instrumental duo