Don't confuse 躁 (zào, restless/impatient) with 燥 (zào, dry). They sound identical but have different meanings. 烦躁 = irritable, 干燥 = dry. Mnemonic: 躁 has 足 (foot) — restless feet; 燥 has 火 (fire) — dry from heat.
usage
Common compounds: 急躁 (jízào, impatient), 烦躁 (fánzào, irritable), 浮躁 (fúzào, superficial and restless), 狂躁 (kuángzào, manic).
