nàn is bound - it does not appear alone. Look for it in disaster/suffering compounds: 灾难 (disaster), 难民 (refugee), 遇难 (to perish), 殉难 (to be martyred), 国难 (national calamity), 难友 (fellow sufferer).
memory
Same character, two readings split by tone: rising nán = the hardship you face daily (a 难题, a 难关); falling nàn = the catastrophe that strikes you (a 灾难, a 劫难). Falling tone, falling fortune.
Left indexing radical 又 - a stylised right hand, two strokes. In simplified 难 this 又 replaces the complex left side of traditional 難. The nàn reading shares the same graph as nán; only tone distinguishes the two senses.
Right 隹 - a pictograph of a short-tailed bird. Supplies the sound (with tone shift) in both readings. The nàn 'disaster' sense developed from 'something hard to escape', extending the difficulty image to misfortune that befalls a person - a calamity, a refugee fleeing it, a martyr who dies in it.
