Calculating the trajectory of a comet requires difficult mathematical equations that account for gravitational perturbations.
计算彗星轨迹需要解决包含引力摄动的困难数学方程。
Poet Celeste Marchetti argues that traditional forms, far from constraining honest expression, actually sharpen a poet's thinking by forcing difficult, productive choices about word and rhythm that free verse allows a writer to avoid.
From a Cross-Text Connections question · Craft and Structure
Which choice best defines “difficult”?
C — Needing much effort or skill to do or understand. “difficult” means needing much effort or skill to do or understand.
Which word means “needing much effort or skill to do or understand”?
B — difficult. “difficult” means needing much effort or skill to do or understand.
difficult — needing much effort or skill to do or understand. In Chinese: 困难的.
difficult is pronounced /ˈdɪfɪkəlt/.
Calculating the trajectory of a comet requires difficult mathematical equations that account for gravitational perturbations. (计算彗星轨迹需要解决包含引力摄动的困难数学方程。)
challenging, arduous, demanding — all close in meaning to difficult (needing much effort or skill to do or understand).
easy, simple — each the opposite of difficult (needing much effort or skill to do or understand).
Yes. difficult is on the SAT Prep Basic list — the everyday academic words the SAT assumes you already have. The Digital SAT does not test vocabulary in isolation; words like this one are tested through Words in Context questions, where you choose the word that completes a passage most logically and precisely.