What is the difference between istiʿānah (seeking aid), istighāthah (seeking urgent help), and istiʿādhah (seeking refuge)?

These three terms (Isti'anah, Istighathah, Isti'adhah) all relate to seeking refuge and reliance upon Allah.

1. Isti'anah: Seeking Allah's help in matters of this world and the Hereafter, disavowing one's own power and strength, and entrusting all affairs to Him, as stated by Allah Almighty: ﴿So worship Him and rely upon Him.﴾ [Hud:123]. 2. Istighathah: Seeking Allah's succor in hardships and crises, as in His saying: ﴿When you sought aid from your Lord, and He answered you.﴾ [Al-Anfal:9]. 3. Isti'adhah: Seeking protection from evil, and from this is His saying: ﴿So when you recite the Qur'an, [first] seek refuge in Allah from Satan, the expelled [from His mercy].﴾ [An-Nahl:98].