From , from ζηλόω ("to emulate, to be jealous").

• (British, America) IPA: /ˈzɛl.əs/

zealous

1. Full of zeal; ardent, fervent; exhibiting enthusiasm or strong passion.
   • 1791, James Boswell, “(please specify the year)”, in The Life of Samuel Johnson, LL.D. […], London: […] Henry Baldwin, for Charles Dilly, […], →OCLC ↗:

     Johnson was truly zealous for the success of "The Adventurer;" and very soon after his engaging in it, he wrote the following letter:

• (full of zeal) ardent, eager, enthusiastic, fervent, passionate, zealotic

• (antonym(s) of “full of zeal”): apathetic, dispassionate, indifferent, unenthusiastic

• jealous
• zeal
• zealot
• zealotic
• zealotical
• zealotry

• French: zélé
• German: eifrig, begeistert
• Italian: zelante
• Portuguese: zeloso
• Russian: рья́ный
• Spanish: celoso, ferviente