异形

not the usual type / atypical / heterotype

different / other / hetero- / unusual / strange / surprising / to distinguish / to separate / to discriminate

to appear / to look / form / shape

variant spelling of the same Chinese word, e.g. 筆劃|笔划[bi3 hua4] and 筆畫|笔画[bi3 hua4] / exact synonym and homonym written with different characters

sexual dimorphism

allotropy