The noun diligence means the trait of working carefully with a lot of effort.
Synonyms are vigor, quickness, earnestness, or keenness.
The word origins from Old French diligence meaning “attention, care, haste, speed”. It also sources directly from Latin diligentia meaning “attentiveness, carefulness” and diligentem meaning “attentive, assiduous, careful”. It also comes from the present-participle adjective from diligere meaning “single out, value highly, esteem, prize, love, aspire to, be content with, appreciate”, originally “to pick out, select”. It comes from dis– meaning “apart” plus legere meaning “choose, gather”.
They need more diligence in analyzing the project.
That student showed great diligence on his studies.
The rookie’s utmost diligence amazed me.